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Are Megabats Big?
Abstract
Traditionally, bats (Order Chiroptera) are divided into two suborders, Megachiroptera (megabats) and Microchiroptera, and this nomenclature suggests a consistent difference in body size. To test whether megabats are, in fact, significantly larger than other bats, we compared them with respect to average body mass (log transformed), using both conventional and phylogenetic statistics. Because bat phylogeny is controversial, including the position of megabats, we employed several analyses. First, we derived two generic-level topologies for 101 genera, one with megabats as the sister of all other bats (morphological tree), the other with megabats as the sister of one specific group of microbats, the Rhinolophoidea (molecular tree). Second, we used a recently published supertree that allowed us to analyze body mass data for 656 species. In addition, because the way body mass has evolved is generally unknown, we employed several sets of arbitrary branch lengths on both topologies, as well as transformations of the branches intended to mimic particular models of character evolution. Irrespective of the topology or branch lengths used, log body mass showed highly significant phylogenetic signal for both generic and species-level analyses (all P 0.001). Conventional statistics indicated that megabats were indeed larger than other bats (P 0.001). Phylogenetic analyses supported this difference only when performed with certain branch lengths, thus demonstrating that careful consideration of the branch lengths used in a comparative analysis can enhance statistical power. A conventional Levene''s test indicated that log body mass was more variable in megabats as compared with other bats (P=0.075 for generic-level data set, P 0.001 for species-level). A phylogenetic equivalent, which gauges the amount of morphospace occupied (or average minimum rate of evolution) relative to topology and branch lengths specified, indicated no significant difference for the generic analyses, but did indicate a difference for some of the species-level analyses. The ancestral bat is estimated to have been approximately 20–23 g in body mass (95% confidence interval approximately 9–51 g).
... Mode and median values are indicated although little evidence exists that body mass per se exerted any influence in the rapid diversification of bats (Isaac et al. 2005). Hutcheon and Garland (2004) estimated ancestral body mass of the crown group of extant bats between 20 and 23 g, but with exceedingly large confidence intervals (between 9 and 51 g); similarly, Safi et al. (2005) obtained a close point estimate at 19 g. More recently, Giannini et al. (2012), using optimization of continuous characters, reported a narrower and lower-valued interval (10-14 g) that included their observed median for extant bats (at ca. ...
... Here almost all significant variation was associated with subclades of megabats (Table 4). Hutcheon and Garland (2004) posed the relevant question, are megabats big? The bimodal distribution of mass in bats (Fig. 1) is explained by some species of fruitbats being generally much larger than most Bmicrobats( or echolocating bats). ...
... The bimodal distribution of mass in bats (Fig. 1) is explained by some species of fruitbats being generally much larger than most Bmicrobats( or echolocating bats). Hutcheon and Garland (2004) concluded that once phylogeny was considered, in consort with certain branch length values and neutral evolutionary models, the Bsignal^disappeared and Old World fruit bats were no longer distinct with respect to Bmicrobats^ (Hutcheon and Garland 2004). CPO (but see below) suggested that not Bmegabats^as a group, but instead particular groups inside Bmegabats,^explained the most conspicuous portion of chiropteran variation in size. ...
Bats are atypical small mammals. Size is crucial for bats because it affects most aerodynamic variables and several key
echolocation parameters. In turn, scaling relationships of both flight and echolocation have been suggested to constrain bat body
size evolution. Previous studies have found a large phylogenetic effect and the inclusion of early Eocene fossil bats contributed to
recovering idiosyncratic body size change patterns in bats. Here, we test these previous hypotheses of bat body size evolution using a
large, comprehensive supermatrix phylogeny (+800 taxa) to optimize body size and examine changes reconstructed along
branches. Our analysis provides evidence of rapid stem phyletic nanism, an ancestral value stabilized at 12 g for crown-clade
Chiroptera followed by backbone stasis, low-magnitude changes inside established families, and massive body size increase at
accelerated rate in pteropodid subclades. Total variation amount explained by pteropodid subclades was 86.3%, with most
changes reconstructed as phyletic increases but also apomorphic decreases. We evaluate these macroevolutionary patterns in
light of the constraints hypothesis, and in terms of both neutral and adaptive evolutionary models. The reconstructed macroevolution
of bat body size led us to propose that echolocation and flight work as successive, nested constraints limiting bat evolution
along the body size scale.
... Habersetzer and Storch (1987) estimated weight of various Eocene bat species and noted that they varied from 7-10 g in Palaeochiropteryx tupaiodon to up to 65 g in Hassianycteris magna. Hutcheon and Garland (2004) attempted to quantify the evolution of size variation in bats with a focus on the question of whether megabats (¼ Pteropodidae), the group including the largest representatives of Chiroptera, were actually larger as a group than other bats (collectively, the microbats) when considering the evolutionary history of bats. Hutcheon and Garland (2004) concluded that megabats indeed tended to be larger than microbats, although specific results were rather ambiguous and varied extensively across analytical methods applied. ...
... Hutcheon and Garland (2004) attempted to quantify the evolution of size variation in bats with a focus on the question of whether megabats (¼ Pteropodidae), the group including the largest representatives of Chiroptera, were actually larger as a group than other bats (collectively, the microbats) when considering the evolutionary history of bats. Hutcheon and Garland (2004) concluded that megabats indeed tended to be larger than microbats, although specific results were rather ambiguous and varied extensively across analytical methods applied. They also gave point estimates of the size of the ancestral bat between 20 and 23 g, but with wide (9-51 g) confidence intervals for these values (Hutcheon and Garland, 2004). ...
... Hutcheon and Garland (2004) concluded that megabats indeed tended to be larger than microbats, although specific results were rather ambiguous and varied extensively across analytical methods applied. They also gave point estimates of the size of the ancestral bat between 20 and 23 g, but with wide (9-51 g) confidence intervals for these values (Hutcheon and Garland, 2004). ...
Size is the single most important factor affecting physiology, locomotion, ecology and behavior of mammals (MacNab, 2007 and citations therein). Understanding evolution of size is important in all organisms, but especially so in cases like bats which exhibit many energetically expensive behaviors (e.g., powered flight, echolocation, long-distance migration), as well as characteristics that represent extreme energy-saving mechanisms (e.g., torpor and hibernation). Most bat species are small: from data in Smith et al. (2004), the central tendency in size in extant bats, as estimated by the median value, is around 14 g (Figure 16.1). However, size in bats as a group spans three orders of magnitude, ranging from 2–3 g (e.g., Craseonycteris, Thyroptera, Furipterus, some vespertilionids; Smith et al., 2004) to a few species exceeding 1 kg (e.g., Acerodon jubatus, Pteropus vampyrus; Kunz and Pierson, 1994). This variation in size scales a number of fundamental traits in bats, including physiological features (e.g., basal metabolic rate; McNab and Bonaccorso, 2001; MacNab, 2003, Speakman and Thomas, 2003); aerodynamic performance (Norberg, 1986, 1990; Rayner, 1986; Watts et al., 2001); dimensions of limb bones and their biomechanical properties (Swartz, 1997, 1998; Swartz and Middleton, 2008); behaviors (e.g., extreme dietary habits like carnivory; Norberg and Fenton, 1988); echolocation call parameters (Jones, 1999); and most life-history traits (e.g., litter mass; Hayssen and Kunz, 1996). These traits likely have an important phylogenetic component of variation, as has been shown, for instance, for the relationship of basal metabolic rate to body mass (Cruz-Neto et al., 2001; cf. MacNab, 2007). Besides the many dependent variables responding to body mass in various ways, size is a fundamental trait that should be understood by itself as an evolving character in bat lineages.
... We use phylogenetic comparative methods to estimate the rate of morphological evolution in reef and nonreef species, which under a Brownian motion model can be viewed as an estimate of disparity that takes into account the effect of time and phylogeny (Hutcheon and Garland 2004;O'Meara et al. 2006). Our approach takes into account uncertainty in the phylogeny (topology and branch lengths) by sampling from the Bayesian posterior distribution of trees (from Tavera et al. 2012), in the history of reefdwelling by using stochastic character mapping (Nielsen 2002;Huelsenbeck et al. 2003) and finally in model choice by using model averaging (Burnham and Anderson 2002). ...
... In a phylogenetic context, morphological diversity or disparity is frequently measured as the rate parameter from a Brownian motion model of phenotypic evolution (see Hutcheon and Garland 2004;O'Meara et al. 2006;Thomas et al. 2006). The faster the Brownian rate, the more morphological diversity among lineages is generated per unit of time. ...
The relationship between habitat complexity and species richness is well established but comparatively little is known about the evolution of morphological diversity in complex habitats. Reefs are structurally complex, highly productive shallow-water marine ecosystems found in tropical (coral reefs) and temperate zones (rocky reefs) that harbor exceptional levels of biodiversity. We investigated whether reef habitats promote the evolution of morphological diversity in the feeding and locomotion systems of grunts (Haemulidae), a group of predominantly nocturnal fishes that live on both temperate and tropical reefs. Using phylogenetic comparative methods and statistical analyses that take into account uncertainty in phylogeny and the evolutionary history of reef living, we demonstrate that rates of morphological evolution are faster in reef-dwelling haemulids. The magnitude of this effect depends on the type of trait; on average, traits involved in the functional systems for prey capture and processing evolve twice as fast on reefs as locomotor traits. This result, along with the observation that haemulids do not exploit unique feeding niches on reefs, suggests that fine-scale trophic niche partitioning and character displacement may be driving higher rates of morphological evolution. Whatever the cause, there is growing evidence that reef habitats stimulate morphological and functional diversification in teleost fishes.
... The age of the association between the habitat and its community is particularly important, as under a Brownian motion (BM) model, trait disparity is expected to accumulate in proportion to time. For each habitat we estimate the BM rate of morphological evolution across the traits mapped onto the phylogeny, which is a time-and phylogeny-corrected estimate of disparity (see Hutcheon & Garland 2004;OÕMeara et al. 2006). We also perform a second analysis to determine if the observed rate changes are also associated with the occupation of novel morphospace by projecting the phylogeny into the morphospace (phylomorphospace sensu Sidlauskas 2007). ...
... There are many ways to estimate morphological diversity (see review by Ciampaglio et al. 2001). In the phylogenetic context it is frequently measured as the rate parameter from a BM model of phenotypic evolution (see Hutcheon & Garland 2004;OÕMeara et al. 2006;Thomas et al. 2006): the faster the Brownian rate the more morphological diversity is generated per unit of time. Therefore, we chose to estimate the rate of morphological evolution in coral reef and non-reef fishes using a BM model of evolution. ...
Ecology Letters (2011) 14: 462–469
Although coral reefs are renowned biodiversity hotspots it is not known whether they also promote the evolution of exceptional ecomorphological diversity. We investigated this question by analysing a large functional morphological dataset of trophic characters within Labridae, a highly diverse group of fishes. Using an analysis that accounts for species relationships, the time available for diversification and model uncertainty we show that coral reef species have evolved functional morphological diversity twice as fast as non-reef species. In addition, coral reef species occupy 68.6% more trophic morphospace than non-reef species. Our results suggest that coral reef habitats promote the evolution of both trophic novelty and morphological diversity within fishes. Thus, the preservation of coral reefs is necessary, not only to safeguard current biological diversity but also to conserve the underlying mechanisms that can produce functional diversity in future.
... We employed both conventional and phylogenetic analyses (e.g., see Garland et al. 1993, 1999, 2005; Clobert et al. 1998; Freckleton et al. 2002; Hutcheon and Garland 2004; Duncan et al. 2007). The latter involved several approaches. ...
... As a test for the adequacy of branch lengths, we regressed the absolute values of standardized contrasts against their standard deviations (Garland et al. 1992). We also compared the means of the absolute values of standardized contrasts between passerines and other birds to test for differences in rates of evolution (Garland 1992; Garland and Ives 2000; Hutcheon and Garland 2004; O'Meara et al. 2006). To determine whether phylogenetic signal was present for log mass, log mass-adjusted M sum , or winter temperature, we used the randomization test for the mean-squared error as described in Blomberg et al. (2003, Matlab program PHYSIG_LL.m). ...
Summit metabolic rate (M(sum), maximum cold-induced metabolic rate) is positively correlated with cold tolerance in birds, suggesting that high M(sum) is important for residency in cold climates. However, the phylogenetic distribution of high M(sum) among birds and the impact of its evolution on current distributions are not well understood. Two potential adaptive hypotheses might explain the phylogenetic distribution of high M(sum) among birds. The cold adaptation hypothesis contends that species wintering in cold climates should have higher M(sum) than species wintering in warmer climates. The flight adaptation hypothesis suggests that volant birds might be capable of generating high M(sum) as a byproduct of their muscular capacity for flight; thus, variation in M(sum) should be associated with capacity for sustained flight, one indicator of which is migration. We collected M(sum) data from the literature for 44 bird species and conducted both conventional and phylogenetically informed statistical analyses to examine the predictors of M(sum) variation. Significant phylogenetic signal was present for log body mass, log mass-adjusted M(sum), and average temperature in the winter range. In multiple regression models, log body mass, winter temperature, and clade were significant predictors of log M(sum). These results are consistent with a role for climate in determining M(sum) in birds, but also indicate that phylogenetic signal remains even after accounting for associations indicative of adaptation to winter temperature. Migratory strategy was never a significant predictor of log M(sum) in multiple regressions, a result that is not consistent with the flight adaptation hypothesis.
... We also diagnosed the fit of the Brownian model to the data using the Pearson correlation between the absolute value of standardized contrasts (equal to the magnitude of the difference in character values between two nodes divided by the square root of the branch length separating those nodes) and their standard deviations, each of which is equal to the square root of the branch length for the contrast (Garland et al. 1992). Under the assumption that a character evolves in a Brownian way, standardized contrasts should exhibit no correlation with branch length (Hutcheon and Garland 2004). ...
... Furthermore, we propose that estimates of rates of morphological evolution have broader applicability than estimates of variance. Because the rate of morphological evolution represents a time-and phylogeny-independent measure of morphological diversity, rates can be used to compare morphological diversity in any pair of clades (Garland 1992; Hutcheon and Garland 2004). ...
Evolutionary lineages differ with regard to the variety of forms they exhibit. We investigated whether comparisons of morphological diversity can be used to identify differences in ecological diversity in two sister clades of centrarchid fishes. Species in the Lepomis clade (sunfishes) feed on a wider range of prey items than species in the Micropterus clade (black basses). We quantified disparity in morphology of the feeding apparatus as within-clade variance on principal components and found that Lepomis exhibits 4.4 and 7.4 times more variance than Micropterus on the first two principal components. However, lineages are expected to diversify morphologically and ecologically given enough time, and this pattern could have arisen due to differences in the amount of time each clade has had to accumulate variance. Despite being sister groups, the age of the most recent common ancestor of Lepomis is approximately 14.6 million years ago and its lineages have a total length of 86.4 million years while the age of the most recent common ancestor of Micropterus is only about 8.4 million years ago, and it has a total branch length of 42.9 million years. We used the Brownian motion model of character evolution to test the hypothesis that time of independent evolution of each clade's lineages accounts for differences in morphological disparity and determined that the rates of evolution of the first two principal components are 4.4 and 7.7 times greater in Lepomis. Thus, time and phylogeny do not account for the differences in morphological disparity observed in Lepomis and Micropterus, and other diversity-promoting mechanisms should be investigated.
... Phytophagy and diurnal habits of Pteropodidae are aligned with modifications in their teeth structure and visual orientation. Pteropodid bats also represent the most speciose family of the Old World and hold the largest known bats, commonly known as 'flying-foxes' , some of them reaching 1 kg when adults [18,50]. It is accepted that they have been distinct from other bats since the early Eocene [29]. ...
Background: Diversity patterns result from ecological to evolutionary processes operating at different spatial and temporal scales. Species trait variation determines the spatial scales at which organisms perceive the environment. Despite this knowledge, the coupling of all these factors to understand how diversity is structured is still deficient. Here, we review the role of ecological and evolutionary processes operating across different hierarchically spatial scales to shape diversity patterns of bats—the second largest mammal order and the only mammals with real flight capability.
Main body: We observed that flight development and its provision of increased dispersal ability influenced the diversification, life history, geographic distribution, and local interspecific interactions of bats, differently across multiple spatial scales. Niche packing combined with different flight, foraging and echolocation strategies and differential use of air space allowed the coexistence among bats as well as for an increased diversity supported by the environment. Considering distinct bat species distributions across space due to their functional characteristics, we assert that understanding such characteristics in Chiroptera improves the knowledge on ecological processes at different scales. We also point two main knowledge gaps that limit progress on the knowledge on scale-dependence of ecological and evolutionary processes in bats: a geographical bias, showing that research on bats is mainly done in the New World; and the lack of studies addressing the mesoscale (i.e. landscape and metacommunity scales).
Conclusions: We propose that it is essential to couple spatial scales and different zoogeographical regions along with their functional traits, to address bat diversity patterns and understand how they are distributed across the environment. Understanding how bats perceive space is a complex task: all bats can fly, but their perception of space varies with their biological traits.
... Morphological disparity has commonly been measured as the variance or average pairwise distance between species [44]. The Brownian motion (BM) rate parameter, calculated using a time-calibrated phylogeny, can provide an estimate of the ability of a lineage to generate diversity that takes into account both time and phylogenetic structure [45,46]. Under a BM model, variance is proportional to time, so a faster BM rate of evolution generates greater diversity over the same interval. ...
The diversity of fishes on coral reefs is influenced by the evolution of feeding innovations. For instance, the evolution of an intramandibular jaw joint has aided shifts to corallivory in Chaetodon butterflyfishes following their Miocene colonization of coral reefs. Today, over half of all Chaetodon species consume coral, easily the largest concentration of corallivores in any reef fish family. In contrast with Chaetodon, other chaetodontids, including the long-jawed bannerfishes, remain less intimately associated with coral and mainly consume other invertebrate prey. Here, we test (i) if intramandibular joint (IMJ) evolution in Chaetodon has accelerated feeding morphological diversification, and (ii) if cranial and post-cranial traits were affected similarly. We measured 19 cranial functional morphological traits, gut length and body elongation for 33 Indo-Pacific species. Comparisons of Brownian motion rate parameters revealed that cranial diversification was about four times slower in Chaetodon butterflyfishes with the IMJ than in other chaetodontids. However, the rate of gut length evolution was significantly faster in Chaetodon, with no group-differences for body elongation. The contrasting patterns of cranial and post-cranial morphological evolution stress the importance of comprehensive datasets in ecomorphology. The IMJ appears to enhance coral feeding ability in Chaetodon and represents a design breakthrough that facilitates this trophic strategy. Meanwhile, variation in gut anatomy probably reflects diversity in how coral tissues are procured and assimilated. Bannerfishes, by contrast, retain a relatively unspecialized gut for processing invertebrate prey, but have evolved some of the most extreme cranial mechanical innovations among bony fishes for procuring elusive prey. © 2017 The Author(s) Published by the Royal Society. All rights reserved.
... Following [33], starter branch lengths corresponding to all branches = 1.0, Grafen's arbitrary lengths, Pagel's arbitrary lengths, and Nee's arbitrary lengths were compared in PGLS and RegOU regressions of genome size on N e u. ...
... Correlations and significance levels are presented in table 2. Symbols are as in figure 4. were to evolve longer limbs, heavier muscles and hearts, and higher maximal oxygen consumption, then they might be able to achieve both higher sprint speed and endurance. Phylogenetic methods could also test whether any disparity in phenotypic diversity is greater than expected based on divergence times within the two lineages, thus indicating differences in rates of phenotypic evolution (e.g., Garland 1992;Hutcheon and Garland 2004;O'Meara et al. 2006). ...
Trade-offs are a common focus of study in evolutionary biology and in studies of locomotor physiology and biomechanics. A previous comparative study of 12 species of European lacertid lizards found a statistically significant negative correlation between residual locomotor speed and stamina (controlling for variation in body size), consistent with ideas about trade-offs in performance based on variation in muscle fiber type composition and other subordinate traits. To begin examining the generality of this finding in other groups of squamates, we measured maximal sprint running speed on a high-speed treadmill and endurance at 1.0 km/h (0.28 m/s) in 14 species of North American phrynosomatid lizards, plus a sample of nine additional species to encompass some of the broadscale diversity of lizards. We used both conventional and phylogenetically informed regression analyses to control for some known causes of performance variation (body size, stockiness, body temperature) and then computed residual performance values. We found no evidence for a trade-off between speed and endurance among the 14 phrynosomatids or among the 23 species in the extended data set. Possible explanations for the apparent difference between lacertids and phrynosomatids are discussed.
... Taxa included in the analyses represented members of the fol lowing families -Emballonuridae, Megadermatidae, Mo lo s si dae, Mormoopidae, Noctilionidae, Phyllostomidae, Rhi nolo phidae, and Vespertilionidae. All analyses were run on species means because body mass information was not uniformly available for all taxa -mean species body mass was taken from the macroecological database of mammalian body mass (MOM v3.3 -Smith et al., 2003) for those taxa lacking individual body mass information (for additional discussion of bat body size, scaling and taxonomy see Hutcheon and Garland, 2004;Hutcheon and Kirsch, 2006;Swartz and Middleton, 2008). All analyses were performed on natural log transformed data (Gingerich et al., 1982;Gingerich and Smith, 1984;Gingerich, 2000). ...
Vampyravus orientalis, from the Oligocene of Fayum, Egypt was the first fossil bat described from Africa. It is represented by a single, relatively large humerus from an unknown horizon in the Jebel Qatram Formation Based on regression analyses of skeletal proportions of modern bats, we developed a set of equations to estimate body mass of fossil bats from known skeletal elements in order to test the hypothesis that Vampyravus could have been within the body size range or other Fayum bats, including several recently described taxa from the Jebel Qatrani and underlying Birket Qarun Formations. Our findings indicate that only Witwatia could have had a body mass similar to Vampyravus Witwatia is known only from Quarry BQ-2 (Late Eocene, Priabonian) in the Birket Qarun Formation Therefore Vampyravus is between 2 and 7 million years younger, depending on where within the Jebel Qatrani Formation it was found Also, a recently discovered distal humerus of Witwatia from BQ-2 demonstrates that this taxon differs substantially from Vampyravus in comparable morphology Vampyravus is distinct from all other Fayum fossil bats Vampyravus shares characteristics of the proximal and distal humerus with several extant bat groups including phyllostomids, some rhinolophoids, natalids, emballonurids, and rhinopomatids The latter two families are represented by fossil forms in the Fayum Although Vampyravus is much larger than either the Fayum emballonurid or rhinopomatid, relatively large size typifies many taxa representing modern bat groups in the Fayum, making it all the more conceivable that Vampyravus could belong to one of these families
... Taxa included in the analyses represented members of the fol lowing families -Emballonuridae, Megadermatidae, Mo lo s si dae, Mormoopidae, Noctilionidae, Phyllostomidae, Rhi nolo phidae, and Vespertilionidae. All analyses were run on species means because body mass information was not uniformly available for all taxa -mean species body mass was taken from the macroecological database of mammalian body mass (MOM v3.3 -Smith et al., 2003) for those taxa lacking individual body mass information (for additional discussion of bat body size, scaling and taxonomy see Hutcheon and Garland, 2004;Hutcheon and Kirsch, 2006;Swartz and Middleton, 2008). All analyses were performed on natural log transformed data (Gingerich et al., 1982;Gingerich and Smith, 1984;Gingerich, 2000). ...
Vampyravus orientalis, from the Oligocene of Fayum, Egypt was the first fossil bat described from Africa. It is represented by a single, relatively large humerus from an unknown horizon in the Jebel Qatrani Formation. Based on regression analyses of skeletal proportions of modern bats, we developed a set of equations to estimate body mass of fossil bats from known skeletal elements in order to test the hypothesis that Vampyravus could have been within the body size range of other Fayum bats, including several recently described taxa from the Jebel Qatrani and underlying Birket Qarun Formations. Our findings indicate that only Witwatia could have had a body mass similar to Vampyravus. Witwatia is known only from Quarry BQ-2 (Late Eocene, Priabonian) in the Birket Qarun Formation. Therefore Vampyravus is between 2 and 7 million years younger, depending on where within the Jebel Qatrani Formation it was found. Also, a recently discovered distal humerus of Witwatia from BQ-2 demonstrates that this taxon differs substantially from Vampyravus in comparable morphology. Vampyravus is distinct from all other Fayum fossil bats. Vampyravus shares characteristics of the proximal and distal humerus with several extant bat groups including phyllostomids, some rhinolophoids, natalids, emballonurids, and rhinopomatids. The latter two families are represented by fossil forms in the Fayum. Although Vampyravus is much larger than either the Fayum emballonurid or rhinopomatid, relatively large size typifies many taxa representing modern bat groups in the Fayum, making it all the more conceivable that Vampyravus could belong to one of these families.
... Pteropodidae exhibits numerous innovations when compared to their closest relatives (Rhinolophoidea and Yangochiroptera), including primary phytophagy and predominance of visual over acoustic orientation (for an extensive list of differences between megabats and microbats see [67]). Also in accordance with ecological adaptation as a drive to diversification is the marked morphological diversity of megabats, such as the high variance in body size, as compared to the other bat families [68] and the independent evolution of nectarivorous habits and associated morphological adaptations in several of the pteropodid clades. Among the demographic causes of explosive radiations are small population sizes (favoring differentiation through genetic drift) and/or the existence of isolated peripheral populations. ...
The family Pteropodidae comprises bats commonly known as megabats or Old World fruit bats. Molecular phylogenetic studies of pteropodids have provided considerable insight into intrafamilial relationships, but these studies have included only a fraction of the extant diversity (a maximum of 26 out of the 46 currently recognized genera) and have failed to resolve deep relationships among internal clades. Here we readdress the systematics of pteropodids by applying a strategy to try to resolve ancient relationships within Pteropodidae, while providing further insight into subgroup membership, by 1) increasing the taxonomic sample to 42 genera; 2) increasing the number of characters (to >8,000 bp) and nuclear genomic representation; 3) minimizing missing data; 4) controlling for sequence bias; and 5) using appropriate data partitioning and models of sequence evolution.
Our analyses recovered six principal clades and one additional independent lineage (consisting of a single genus) within Pteropodidae. Reciprocal monophyly of these groups was highly supported and generally congruent among the different methods and datasets used. Likewise, most relationships within these principal clades were well resolved and statistically supported. Relationships among the 7 principal groups, however, were poorly supported in all analyses. This result could not be explained by any detectable systematic bias in the data or incongruence among loci. The SOWH test confirmed that basal branches' lengths were not different from zero, which points to closely-spaced cladogenesis as the most likely explanation for the poor resolution of the deep pteropodid relationships. Simulations suggest that an increase in the amount of sequence data is likely to solve this problem.
The phylogenetic hypothesis generated here provides a robust framework for a revised cladistic classification of Pteropodidae into subfamilies and tribes and will greatly contribute to the understanding of character evolution and biogeography of pteropodids. The inability of our data to resolve the deepest relationships of the major pteropodid lineages suggests an explosive diversification soon after origin of the crown pteropodids. Several characteristics of pteropodids are consistent with this conclusion, including high species diversity, great morphological diversity, and presence of key innovations in relation to their sister group.
... Despite innovations being a central theme in the discussion of morphological diversity (Liem 1973; Vermeij 1973), studies that address the link between innovations and morphological diversity, which also take into account the potentially confounding effects of time and phylogeny on the calculation of disparity, are rare. The scarcity of such studies is perhaps explained by the recent development of the statistical methods to incorporate phylogeny into the measures of morphological diversity (Foote 1997; Hutcheon and Garland 2004; O'Meara et al. 2006) and the time and effort needed to measure a variety of morphological traits across a large number of species (with and without the innovation) and to generate a time-calibrated phylogeny. ...
The association between diversification and evolutionary innovations has been well documented and tested in studies of taxonomic richness but the impact that such innovations have on the diversity of form and function is less well understood. Using phylogenetically rigorous techniques, we investigated the association between morphological diversity and two design breakthroughs within the jaws of parrotfish. Similar intramandibular joints and other modifications of the pharyngeal jaws have evolved repeatedly in teleost fish and are frequently hypothesized to promote diversity. We quantified morphological diversity within six functionally important oral jaw traits using the Brownian motion rate of evolution to correct for phylogenetic and time-related biases and compared these rates across clades that did and did not possess the intramandibular joint and the parrotfish pharyngeal jaw. No change in morphological diversity was associated with the pharyngeal jaw modification alone but rates of oral jaw diversification were up to 8× faster in parrotfish species that possessed both innovations. Interestingly, this morphological diversity may not have led to differential resource uses as available data suggest that members of this clade show remarkable homogeneity of diet.
... In addition to the simulation-based tests described below, the hypothesis that the anostomoid sample variance equaled the curimatoid sample variance was tested with Levene's test, which is preferred over the F-test when the measured distributions cannot be assumed to be normal (Van Valen 1978;Garland et al. 1993;Hutcheon and Garland 2004), at a 95% critical value. Neither Levene's test nor the F-test, however, accounts for the dependence of datapoints (species) on the underlying phylogenetic structure. ...
This study develops the random phylogenies rate test (RAPRATE), a likelihood method that simulates morphological evolution along randomly generated phylogenies, and uses it to determine whether a considerable difference in morphological diversity between two sister clades of South American fishes should be taken as evidence of differing rates of morphological change or lineage turnover. Despite identical ages of origin, similar species richness, and sympatric geographic distributions, the morphological and ecological diversity of the superfamily Anostomoidea exceeds that of the Curimatoidea. The test shows with 90% confidence (using variance among species as the measure of morphological diversity) or 99% confidence (using volume of occupied morphospace) that the rate of morphological change per unit time in the Anostomoidea likely exceeded that of the Curimatoidea. Variation in the rate of lineage turnover (speciation and extinction rates) is not found to affect greatly the morphological diversity of simulated clades and is not a likely explanation of the observed difference in morphological diversity in this case study. Though a 17% or greater delay in the onset of diversification in the Curimatoidea remains a possible alternative explanation of unequal morphological diversification, further simulations suggest that two clades drawn from the possible treespace of the Anostomoidea and Curimatoidea will rarely differ so greatly in the onset of diversification. Several uniquely derived morphological and ecological features of the Anostomoidea and Curimatoidea may have accelerated or decelerated their rate of morphological change, including a marked lengthening of the quadrate that may have relaxed structural constraints on the evolution of the anostomoid jaw.
This second volume completes the unique survey of North American Tertiary mammals, and covers all the remaining taxa not contained in Volume 1. It provides a complete listing of mammalian diversity over time and space, and evaluates the effect of biogeography and climatic change on evolutionary patterns and faunal transitions, with the distribution in time and space of each taxon laid out in a standardized format. It contains six summary chapters that integrate systematic and biogeographic information for higher taxa, and provides a detailed account of the patterns of occurrence for different species at hundreds of different fossil localities, with the inclusion of many more localities than were contained in the first volume. With over thirty chapters, each written by leading authorities, and an addendum that updates the occurrence and systematics of all of the groups covered in Volume 1, this will be a valuable reference for paleontologists and zoologists.
This second volume completes the unique survey of North American Tertiary mammals, and covers all the remaining taxa not contained in Volume 1. It provides a complete listing of mammalian diversity over time and space, and evaluates the effect of biogeography and climatic change on evolutionary patterns and faunal transitions, with the distribution in time and space of each taxon laid out in a standardized format. It contains six summary chapters that integrate systematic and biogeographic information for higher taxa, and provides a detailed account of the patterns of occurrence for different species at hundreds of different fossil localities, with the inclusion of many more localities than were contained in the first volume. With over thirty chapters, each written by leading authorities, and an addendum that updates the occurrence and systematics of all of the groups covered in Volume 1, this will be a valuable reference for paleontologists and zoologists.
Bats, quoted as sleeping for up to 20h a day, are an often used example of extreme sleep duration amongst mammals. Given that duration has historically been one of the primary metrics featured in comparative studies of sleep, it is important that species specific sleep durations are well founded. Here, we re-examined the evidence for the characterisation of bats as extreme sleepers and discuss whether it provides a useful representation of the sleep behaviour of Chiroptera. Although there are a wealth of activity data to suggest that the diurnal cycle of bats is dominated by rest, estimates of sleep time generated from electrophysiological analyses suggest considerable interspecific variation, ranging from 83% to a more moderate 61% of the 24h day spent asleep. Temperature dependent changes in the duration and electroencephalographic profile of sleep suggest that bats represent a unique model for investigating the relationship between sleep and torpor. Further sources of intra-specific variation in sleep duration, including the impact of artificial laboratory environments and sleep intensity, remain unexplored. Future studies conducted in naturalistic environments, using larger sample sizes and relying on a pre-determined set of defining criteria will undoubtedly provide novel insights into sleep in bats and other species.
Bats are unique among mammals in that they have evolved the capacity to fly. This has generated strong selective pressure on the morphology and function of their digestive system. Given that in bats intestinal length and nominal surface-area are proportional to body mass, this trait importantly relates to explaining some of their digestive characteristics. We described the relationship between digestive traits and body mass of four species of bats of the family Vespertilionidae living in a montane ecosystem in central Mexico. We calculated food transit time, apparent dry matter digestibility, and defecation rate in feeding trials under captive conditions. We also: 1) built a model of the relationship between digestive traits and body mass to determine if this association was consistent within the members of the family Vespertilionidae, and 2) mapped these traits along the phylogeny to explore how digestive characteristics may have evolved. In our feeding trials, body mass was positively related to transit time and negatively related to apparent dry matter digestibility. The model predicted accurately the transit time in bats with body mass < 20 g. The phylogenetic approach suggested that over the evolutionary history of the family, transit time decreased as digestibility increased. Because of the results obtained here, it is likely that for most bats of the family Vespertilionidae, adaptations in digestive traits to process food have followed evolutionary changes in their body mass. We discuss these findings in a physiological and ecological context.
• Bats (order Chiroptera) are the only mammals capable of powered flight, and this may be an important factor behind their rapid diversification into the over 1400 species that exist today – around a quarter of all mammalian species. Though flight in bats has been extensively studied, the evolutionary history of the ability to fly in the chiropterans remains unclear.
• We provide an updated synthesis of current understanding of the mechanics of flight in bats (from skeleton to metabolism), its relation to echolocation, and where previously articulated evolutionary hypotheses for the development of flight in bats stand following recent empirical advances. We consider the gliding model, and the echolocation‐first, flight‐first, tandem development, and diurnal frugivore hypotheses. In the light of the recently published description of the web‐winged dinosaur Ambopteryx longibrachium, we draw together all the current evidence into a novel hypothesis.
• We present the interdigital webbing hypothesis: the ancestral bat exhibited interdigital webbing prior to powered flight ability, and the Yangochiroptera, Pteropodidae, and Rhinolophoidea evolved into their current forms along parallel trajectories from this common ancestor. Thus, we suggest that powered flight may have evolved multiple times within the Chiroptera and that similarity in wing morphology in different lineages is driven by convergence from a common ancestor with interdigital webbing.
Evolutionary lineages differ with regard to the variety of forms they exhibit. We investigated whether comparisons of morphological diversity can be used to identify differences in ecological diversity in two sister clades of centrarchid fishes. Species in the Lepomis clade (sunfishes) feed on a wider range of prey items than species in the Micropterus clade (black basses). We quantified disparity in morphology of the feeding apparatus as within-clade variance on principal components and found that Lepomis exhibits 4.4 and 7.4 times more variance than Micropterus on the first two principal components. However, lineages are expected to diversify morphologically and ecologically given enough time, and this pattern could have arisen due to differences in the amount of time each clade has had to accumulate variance. Despite being sister groups, the age of the most recent common ancestor of Lepomis is approximately 14.6 million years ago and its lineages have a total length of 86.4 million years while the age of the most recent common ancestor of Micropterus is only about 8.4 million years ago, and it has a total branch length of 42.9 million years. We used the Brownian motion model of character evolution to test the hypothesis that time of independent evolution of each clade's lineages accounts for differences in morphological disparity and determined that the rates of evolution of the first two principal components are 4.4 and 7.7 times greater in Lepomis. Thus, time and phylogeny do not account for the differences in morphological disparity observed in Lepomis and Micropterus, and other diversity-promoting mechanisms should be investigated.
INTRODUCTION With the exception of rodents, bats are the most diverse extant mammalian order. The fossil record of bats is notoriously poor, however. There are several good reasons for the impoverished fossil record of chiropterans. Bats are generally quite small mammals with very light and delicate bones. They are volant (the only mammals to achieve powered flight) and typically roost in trees and caves away from areas conducive to long-term sedimentary accumulation. Their taxonomic diversity increases dramatically toward the equator, especially in tropical rain forests that have a depauperate fossil record for their entire biota. The Pleistocene fossil record for bats is much better than that for the Tertiary, but it is mostly restricted to cave deposits and extant, cave-adapted species. Prior to the Pleistocene, the fossil record of bats is too incomplete to provide a comprehensive picture of their evolution. With the exception of the exquisite examples from the Quercy Phosphorites, Geiseltal Coal Deposits, Green River Formation, and the Messel Oil Shales (Gunnell, 2001; Storch, 2001), diagnostic remains of bats are more tantalizing than informative. Typical Tertiary bat fossils are isolated teeth, jaw fragments, or portions of long bones. Unfortunately, the primitive and still widespread dilambdodont dentition of insectivorous bats is not highly distinctive and has appeared in a number of mammalian groups. This problem perplexes paleontologists attempting to identify fossils. In particular, the fossil teeth of various Insectivora and Chiroptera are often confused. There are probably good bats represented among the many taxa of Paleocene insectivorous mammals.
Previous work has shown that the relative proportions of wing components (i.e., humerus, ulna, carpometacarpus) in birds are related to function and ecology, but these have rarely been investigated in a phylogenetic context. Waterbirds including “Pelecaniformes”, Ciconiiformes, Procellariiformes, Sphenisciformes and Gaviiformes form a highly supported clade and developed a great diversity of wing forms and foraging ecologies. In this study, forelimb disparity in the waterbird clade was assessed in a phylogenetic context. Phylogenetic signal was assessed via Pagel's lambda, Blomberg's K and permutation tests. We find that different waterbird clades are clearly separated based on forelimb component proportions, which are significantly correlated with phylogeny but not with flight style. Most of the traditional contents of “Pelecaniformes” (e.g., pelicans, cormorants and boobies) cluster with Ciconiiformes (herons and storks) and occupy a reduced morphospace. These taxa are closely related phylogenetically but exhibit a wide range of ecologies and flight styles. Procellariiformes (e.g. petrels, albatross, and shearwaters) occupy a wide range of morphospace, characterized primarily by variation in the relative length of carpometacarpus and ulna. Gaviiformes (loons) surprisingly occupy a wing morphospace closest to diving petrels and penguins. Whether this result may reflect wing proportions plesiomorphic for the waterbird clade or a functional signal is unclear. A Bayesian approach detecting significant rate shifts across phylogeny recovered two such shifts. At the base of the two sister clades Sphenisciformes + Procellariiformes, a shift to an increase evolutionary rate of change is inferred for the ulna and carpometacarpus. Thus, changes in wing shape begin prior to the loss of flight in the wing-propelled diving clade. Several shifts to slower rate of change are recovered within stem penguins.This article is protected by copyright. All rights reserved.
A fundamental goal of evolutionary ecology is understanding the processes responsible for contemporary patterns of morphological diversity and species richness. Transitions across the marine–freshwater interface are regarded as key triggers for adaptive radiation of many clades. Using the Australian terapontid fish family as a model system we employed phylogenetic analyses to compare the rates of ecological (dietary) and mor-phological evolution between marine and freshwater species of the family. Results sug-gested significantly higher rates of phenotypic evolution in key dietary and morphological characters in freshwater species compared to marine counterparts. Moreover, there was
Little is known about vegetative morphological diversification in Neotropical plant clades in comparison with diversification of reproductive characters. Phylogenetic relationships of the Neotropical Heliotropium (Heliotropiaceae) were studied using sequences of nrITS and four plastid regions (trnL-trnF, trnS-trnG, trnH-psbA, rps16). Vegetative morphological diversity (leaf morphology, habit), measured as amount of morphospace occupied and as variance of individual characters, was compared among the clades resolved and between groups of species inhabiting dry and humid areas. Three well-supported clades were recovered: (1) Heliotropium sect. Heliothamnus from the tropical Andes; (2) Heliotropium sect. Cochranea from the Peruvian and the Atacama Deserts; and (3) the Tournefortia clade, comprising the remaining American sections of Heliotropium and the mainly Neotropical Tournefortia sect. Tournefortia. Phylogenetic discordance detected between the plastid and nuclear partitions may have been due to lineage sorting, hybridization or differences in number of informative sites. Morphological diversity was largest in the Tournefortia clade and tended to be greater in dry than in humid areas, but without statistical sup port. Heliotropium sect. Cochranea was as diverse as the Tournefortia clade in leaf morphology and may have experienced adaptive radiation in the Atacama Desert. Lowest vegetative diversity was found in Heliotropium sect. Heliothamnus. The infrageneric delimitation in Heliotropium needs reassessment.
Recent comparative-method and molecular studies have called into question both the classic subordinal division of bats into Megachiroptera versus Microchiroptera and the infraordinal separation of microchiropterans as Yinochiroptera and Yangochiroptera: megabats are not necessarily large, nor are microbats uniformly small; some yinochiropterans may be specially related to megachiropterans whilst others are more nearly affiliated with yangochiropterans; and quite apart from the conflict with DNA comparisons, the microbat dichotomy (based on moveable versus fused premaxillae) is neither completely cladistic nor parsimonious. We conclude that current appellations — including the neologism Yinpterochiroptera — no longer embody the authors' intended groups or have been so frequently redefined as to be positively misleading. We therefore adopt the new subordinal names Vespertilioniformes (for the group including Emballonuridae, Nycteridae, and the ‘yangochiropterans’) and Pteropodiformes (for the taxon comprised of Craseonycteridae, Hipposideridae, Megadermatidae, Rhinolophidae, Rhinopomatidae, and Pteropodidae). These epithets are ultimately based on the oldest valid generic names for included taxa (respectively Vespertilio Linnaeus, 1758 and Pteropus Brisson, 1762), and are thus impervious to pre-emption or misinterpretation.
Extensive skeletal pneumaticity (air-filled bone) is a distinguishing feature of birds. The proportion of the skeleton that is pneumatized varies considerably among the >10,000 living species, with notable patterns including increases in larger bodied forms, and reductions in birds employing underwater pursuit diving as a foraging strategy. I assess the relationship between skeletal pneumaticity and body mass and foraging ecology, using a dataset of the diverse "waterbird" clade that encompasses a broad range of trait variation. Inferred changes in pneumaticity and body mass are congruent across different estimates of phylogeny, whereas pursuit diving has evolved independently between two and five times. Phylogenetic regressions detected positive relationships between body mass and pneumaticity, and negative relationships between pursuit diving and pneumaticity, whether independent variables are considered in isolation or jointly. Results are generally consistent across different estimates of topology and branch lengths. "Predictive" analyses reveal that several pursuit divers (loons, penguins, cormorants, darters) are significantly apneumatic compared to their relatives, and provide an example of how phylogenetic information can increase the statistical power to detect taxa that depart from established trait correlations. These findings provide the strongest quantitative comparative support yet for classical hypotheses regarding the evolution of avian skeletal pneumaticity.
Quantifying rates of morphological evolution is important in many macroevolutionary studies, and critical when assessing possible adaptive radiations and episodes of punctuated equilibrium in the fossil record. However, studies of morphological rates of change have lagged behind those on taxonomic diversification, and most authors have focused on continuous characters and quantifying patterns of morphological rates over time. Here, we provide a phylogenetic approach, using discrete characters and three statistical tests to determine points on a cladogram (branches or entire clades) that are characterized by significantly high or low rates of change. These methods include a randomization approach that identifies branches with significantly high rates and likelihood ratio tests that pinpoint either branches or clades that have significantly higher or lower rates than the pooled rate of the remainder of the tree. As a test case for these methods, we analyze a discrete character dataset of lungfish, which have long been regarded as "living fossils" due to an apparent slowdown in rates since the Devonian. We find that morphological rates are highly heterogeneous across the phylogeny and recover a general pattern of decreasing rates along the phylogenetic backbone toward living taxa, from the Devonian until the present. Compared with previous work, we are able to report a more nuanced picture of lungfish evolution using these new methods.
Mechanisms underlying the dramatic patterns of genome size variation across the tree of life remain mysterious. Effective population size (N(e)) has been proposed as a major driver of genome size: selection is expected to efficiently weed out deleterious mutations increasing genome size in lineages with large (but not small) N(e). Strong support for this model was claimed from a comparative analysis of N(e)u and genome size for ≈30 phylogenetically diverse species ranging from bacteria to vertebrates, but analyses at that scale have so far failed to account for phylogenetic nonindependence of species. In our reanalysis, accounting for phylogenetic history substantially altered the perceived strength of the relationship between N(e)u and genomic attributes: there were no statistically significant associations between N(e)u and gene number, intron size, intron number, the half-life of gene duplicates, transposon number, transposons as a fraction of the genome, or overall genome size. We conclude that current datasets do not support the hypothesis of a mechanistic connection between N(e) and these genomic attributes, and we suggest that further progress requires larger datasets, phylogenetic comparative methods, more robust estimators of genetic drift, and a multivariate approach that accounts for correlations between putative explanatory variables.
When the morphological diversity of a clade of species is quantified as the among-species variance in morphology, that diversity is a joint consequence of the phylogenetic structure of the clade (i.e., temporal pattern of speciation events) and the rates of change in the morphological traits of interest. Extrinsic factors have previously been linked to variation in the rate of morphological change among clades. Here, we ask whether species co-occurrence is positively correlated with the rate of change in several ecologically relevant morphological characters using the North American freshwater fish clade Percina (Teleostei: Etheostomatinae). We constructed a time-calibrated phylogenetic tree of Percina from mtDNA sequence data, gathered data on eight morphological characters from 37 species, used a principal components analysis to identify the primary axes of morphological variation, and analyzed 16,094 collection records to estimate species co-occurrence. We then calculated standardized independent contrasts (SIC) of the morphological traits (rate of change) at each node, estimated ancestral species co-occurrence, and quantified the correlation between species co-occurrence and rate of morphological change. We find that morphology changes more quickly when co-occurrence is greater in Percina. Our results provide strong evidence that co-occurrence among close relatives is linked to the morphological diversification of this clade.
Over the past two decades, comparative biological analyses have undergone profound changes with the incorporation of rigorous evolutionary perspectives and phylogenetic information. This change followed in large part from the realization that traditional methods of statistical analysis tacitly assumed independence of all observations, when in fact biological groups such as species are differentially related to each other according to their evolutionary history. New phylogenetically based analytical methods were then rapidly developed, incorporated into ;the comparative method', and applied to many physiological, biochemical, morphological and behavioral investigations. We now review the rationale for including phylogenetic information in comparative studies and briefly discuss three methods for doing this (independent contrasts, generalized least-squares models, and Monte Carlo computer simulations). We discuss when and how to use phylogenetic information in comparative studies and provide several examples in which it has been helpful, or even crucial, to a comparative analysis. We also consider some difficulties with phylogenetically based statistical methods, and of comparative approaches in general, both practical and theoretical. It is our personal opinion that the incorporation of phylogeny information into comparative studies has been highly beneficial, not only because it can improve the reliability of statistical inferences, but also because it continually emphasizes the potential importance of past evolutionary history in determining current form and function.
Morphological diversity is routinely used to infer ecological variation among species because differences in form underlie variation in functional performance of ecological tasks like capturing prey, avoiding predators, or defending territories. However, many functions have complex morphological bases that can weaken associations between morphological and functional diversification. We investigate the link between these levels of diversity in a mechanically explicit model of fish suction-feeding performance, where the map of head morphology to feeding mechanics is many-to-one: multiple, alternative forms can produce the same mechanical property. We show that many-to-one mapping leads to discordance between morphological and mechanical diversity in the freshwater fish family, the Centrarchidae, despite close associations between morphological changes and their mechanical effects. We find that each of the model's five morphological variables underlies evolution of suction capacity. Yet, the major centrarchid clades exhibit an order of magnitude range in diversity of suction mechanics in the absence of any clear difference in diversity of the morphological variables. This cryptic pattern of mechanical diversity suggests an evolutionary history for suction performance that is unlike the one inferred from comparisons of morphological diversity. Because many-to-one mapping is likely to be common in functional systems, this property of design may lead to widespread discordance between functional and morphological diversity. Although we focus on the interaction between morphology and mechanics, many-to-one mapping can decouple diversity between levels of organization in any hierarchical system.
Phyllostomidae is a large (> 140 species), diverse clade of Neotropical bars. Different species in this family feed on blood, insects, vertebrates, nectar, pollen, and fruits. We investigated phylogenetic relationships among all genera of phyllostomid bats and tested monophyly of several genera (e.g., Micronycteris, Mimon, Artibeus, Vampyressa) using 150 morphological, karyological, and molecular characters. Results of parsimony analyses of these combined data indicate that all traditionally recognized phyllostomid subfamilies are monophyletic and that most taxa that share feeding specializations form clades. These results largely agree with studies that have used a taxonomic congruence approach to evaluate karyological, immunological, and limited sets of morphological characters, although our finding that Phyllostominae is monophyletic is novel. Our results indicate that several genera (Micronycteris, Artibeus, and Vampyressa) are not monophyletic. We propose a new classification for Phyllostomidae that better reflects hypothesized evolutionary relationships. Important features of this new classification include: (1) formal recognition of two clades that group nectarivorous and frugivorous subfamilies: respectively, (2) redefinition of Glossophaginae and recognition of two tribal-level taxa within that subfamily, (3) recognition of several tribal-level taxa in Phyllostominae, (4) formal recognition of two clades that have been colloquially referred to as "short-faced" and "long-faced" stenodermatines, (5) elevation of the subgenera of Micronycteris to generic rank, (6) recognition of Mesophylla as a junior synonym of Ectophylla, (7) recognition of Enchisthenes as a distinct genus, and (8) retention of Dermanura and Koopmania as subgenera of Artibeus. Although Vampyressa is not monophyletic in our tree, we recommend no nomenclatural change because we did not include all Vampyressa species in our study. Comparisons of character and taxonomic congruence approaches indicate that character congruence provides improved resolution of relationships among phyllostomids. Many data sets are informative only at limited hierarchical levels or in certain portions of the phyllostomid tree. Although both chromosomal and immunological data provide additional support fur several clades that we identified, these data sets are incongruent with many aspects of our phylogenetic results. These conflicts may be due to methodological constraints associated with the use of karyological and immunological data (e.g., problems with assessing homologies and distinguishing primitive from derived traits). Among other observations, we find that Macrotus waterhousii, which has been thought to have the primitive karyotype for the family, nests well within the phyllostomine clade. This suggests that results of previous analyses of chromosomal data may need to be reevaluated. Mapping characters and behaviors on our phylogenetic tree provides a context for evaluating hypotheses of evolution in Phyllostomidae. Although previous studies of uterine evolution in phyllostomids and other mammals have generally supported the unidirectional progressive fusion hypothesis, our results indicate that intermediate stages of external uterine fusion are often derived relative to the fully simplex condition, and that reversals also occur with respect to internal uterine fusion. Uterine fusion therefore appears to be neither completely unidirectional nor progressive in Phyllostomidae. Evolution of the vibrissae and noseleaf is similarly complex and homoplasy is common in these structures; however, many transformations in these systems diagnose clades of phyllostomids. Within Phyllostomidae, there is considerable derived reduction in numbers of vibrissae present in various vibrissal clusters. The phyllostomid noseleaf seems to have become a much more elaborate and complex structure over evolutionary time. Primitively within the family, the spear was short, the internarial region was flat, and the horseshoe was undifferentiated from the upper lip. Subsequently, within the various subfamilies, the spear became more elongate, the central rib and other internarial structures evolved, and the labial horseshoe became flaplike or cupped in some taxa. Dietary evolution in phyllostomids appears somewhat more complex than previously thought. We find that must of the major dietary guilds (e.g., frugivory, sanguivory) are represented by a single large clade within Phyllostomidae, indicating that each feeding specialization evolved once. However, reversals do occur (e.g., loss of nectar- and pollen-feeding in many phyllostomines and stenodermatines), and some specializations may have evolved more than once (e.g., carnivory).
We propose that the ancestors of bats were small, nocturnal, sylvatic gliders that used echolocation for general orientation. Their echolocation calls were short, low intensity, broadband clicks, which translated into a very short operational range. In the lineage that gave rise to bats, a switch to stronger, tonal signals permitted the use of echolocation to detect, track, and assess flying insects in subcanopy settings. We propose that these animals hunted from perches and used echolocation to detect, track, and assess flying insects, which they attacked while gliding. In this way, the perfection of echolocation for hunting preceded the appearance of flapping flight, which marked the emergence of bats. Flapping flight had appeared by the Eocene when at least eight families are known from the fossil record. Stronger signals and adaptations to minimize self-deafening were central to the perfection of echolocation for locating flying prey. Echolocation constituted a key innovation that permitted the evolution and radiation of bats. At the same time, however, its short effective range imposed a major constraint on the size of bats. This constraint is associated with flight speed and the very small time intervals from detection of, and contact with a flying target. Gleaning and high duty cycle echolocation are two derived approaches to hunting prey in cluttered situations, places where echoes from background and other objects arrive before or at the same time as echoes from prey. Both had appeared by the Eocene.
The aim of this study was to determine if divergence in habitat use among lacertid lizards is paralleled by morphological differentiation. For 35 lacertid species, we measured body, head and limb dimensions. Habitat use was inferred from the literature: ground-dwelling on open terrain, ground-dwelling in vegetated areas, shrub-climbing, tree-climbing, saxicolous (i.e. rock-climbing). Traditional (i.e. non-phylogenetic) statistical analyses suggest morphological differences among species groups with different habitat use. Ground-dwelling species from open habitats tend to have longer femurs, tibiae and humeri (relative to body length) than other groups. Cursorial (i.e. level-running) species have relatively high heads and trunks compared to climbing species. These differences follow biomechanical predictions and it is tempting to consider them as adaptations to habitat use. However, phylogenetic analyses of the data fail to establish a clear relationship between habitat use and morphology in the data set considered. There is a weak indication that the differences in head and trunk height have evolved as an adaptation to different habitat use, but the differences in relative limb dimensions among species groups with different habitat use vanish. Either adaptation of limb dimensions to habitat use has not occurred in lacertid lizards, or our methods are unable to demonstrate such an adaptation. We show that uncertainties in the topology of the phylogenetic tree used are unlikely to influence the outcome of our study. We also address the fact that habitat use is often similar in different branches of the phylogenetic tree, and the consequences this may have for the power of our statistical analyses.
Protein electrophoresis and immunology were used to test hypotheses concerning phylogenetic relationships within the family Emballonuridae and the relationship of the family Rhinopomatidae to the Emballonuridae. These data indicate the presence of three major subdivisions within the family. The eight genera from the New World form one monophyletic group, the Old World genera Taphozous and Saccolaimus form the second, and Emballonura and Coleura the third. The Emballonura-Coleura lineage is more closely related to the New World genera than to the other Old World group. The family Rhinopomatidae was found to be distantly related to both the Emballonuridae and the Vespertilionidae.
The purpose of this data set was to compile body mass information for all mammals on Earth so that we could investigate the patterns of body mass seen across geographic and taxonomic space and evolutionary time. We were interested in the heritability of body size across taxonomic groups (How conserved is body mass within a genus, family, and order?), in the overall pattern of body mass across continents (Do the moments and other descriptive statistics remain the same across geographic space?), and over evolutionary time (How quickly did body mass patterns iterate on the patterns seen today? Were the Pleistocene extinctions size specific on each continent, and did these events coincide with the arrival of man?). These data are also part of a larger project that seeks to integrate body mass patterns across very diverse taxa (NCEAS Working Group on Body Size in Ecology and Paleoecology: linking pattern and process across space, time, and taxonomic scales). We began with the updated version of D. E. Wilson and D. M. Reeder's taxonomic list of all known Recent mammals of the world (N = 4629 species) to which we added status, distribution, and body mass estimates compiled from the primary and secondary literature. Whenever possible, we used an average of male and female body mass, which was in turn averaged over multiple localities to arrive at our species body mass values. The sources are line referenced in the main data set, with the actual references appearing in a table within the metadata. Mammals have individual records for each continent they occur on. Note that our data set is more than an amalgamation of smaller compilations. Although we relied heavily on a data set for Chiroptera by K. E. Jones (N = 905), the CRC handbook of Mammalian Body Mass (N = 688), and a data set compiled for South America by P. Marquet (N = 505), these represent less than half the records in the current database. The remainder are derived from more than 150 other sources. Furthermore, we include a comprehensive late Pleistocene species assemblage for Africa, North and South America, and Australia (an additional 230 species). “Late Pleistocene” is defined as approximately 11 ka for Africa, North and South America, and as 50 ka for Australia, because these times predate anthropogenic impacts on mammalian fauna. Estimates contained within this data set represent a generalized species value, averaged across sexes and geographic space. Consequently, these data are not appropriate for asking population-level questions where the integration of body mass with specific environmental conditions is important. All extant orders of mammals are included, as well as several archaic groups (N = 4859 species). Because some species are found on more than one continent (particularly Chiroptera), there are 5731 entries. We have body masses for the following: Artiodactyla (280 records), Bibymalagasia (2 records), Carnivora (393 records), Cetacea (75 records), Chiroptera (1071 records), Dasyuromorphia (67 records), Dermoptera (3 records), Didelphimorphia (68 records), Diprotodontia (127 records), Hydracoidea (5 records), Insectivora (234 records), Lagomorpha (53 records), Litopterna (2 records), Macroscelidea (14 records), Microbiotheria (1 record), Monotremata (7 records), Notoryctemorphia (1 record), Notoungulata (5 records), Paucituberculata (5 records), Peramelemorphia (24 records), Perissodactyla (47 records), Pholidota (8 records), Primates (276 records), Proboscidea (14 records), Rodentia (1425 records), Scandentia (15 records), Sirenia (6 records), Tubulidentata (1 record), and Xenarthra (75 records).
Bat wing morphology is considered in relation to flight performance and flight behaviour to clarify the functional basis for eco-morphological correlations in flying animals. Bivariate correlations are presented between wing dimensions and body mass for a range of bat families and feeding classes, and principal-components analysis is used to measure overall size, wing size and wing shape. The principal components representing wing size and wing shape (as opposed to overall size) are interpreted as being equivalent to wing loading and to aspect ratio. Relative length and area of the hand-wing or wingtip are determined independently of wing size, and are used to derive a wingtip shape index, which measures the degree of roundedness or pointedness of the wingtip. The optimal wing form for bats adapted for different modes of flight is predicted by means of mechanical and aerodynamic models. We identify and model aspects of performance likely to influence flight adaptation significantly; these include selective pressures for economic forward flight (low energy per unit time or per unit distance (equal to cost of transport)), for flight at high or low speeds, for hovering, and for turning. Turning performance is measured by two quantities: manoeuvrability, referring to the minimum space required for a turn at a given speed; and agility, relating to the rate at which a turn can be initiated. High flight speed correlates with high wing loading, good manoeuvrability is favoured by low wing loading, and turning agility should be associated with fast flight and with high wing loading. Other factors influencing wing adaptations, such as migration, flying with a foetus or young or carrying loads in flight (all of which favour large wing area), flight in cluttered environments (short wings) and modes of landing, are identified. The mechanical predictions are cast into a size-independent principal-components form, and are related to the morphology and the observed flight behaviour of different species and families of bats. In this way we provide a broadly based functional interpretation of the selective forces that influence wing morphology in bats. Measured flight speeds in bats permit testing of these predictions. Comparison of open-field free-flight speeds with morphology confirms that speed correlates with mass, wing loading and wingtip proportions as expected; there is no direct relation between speed and aspect ratio. Some adaptive trends in bat wing morphology are clear from this analysis. Insectivores hunt in a range of different ways, which are reflected in their morphology. Bats hawking high-flying insects have small, pointed wings which give good agility, high flight speeds and low cost of transport. Bats hunting for insects among vegetation, and perhaps gleaning, have very short and rounded wingtips, and often relatively short, broad wings, giving good manoeuvrability at low flight speeds. Many insectivorous species forage by `flycatching' (perching while seeking prey) and have somewhat similar morphology to gleaners. Insectivorous species foraging in more open habitats usually have slightly longer wings, and hence lower cost of transport. Piscivores forage over open stretches of water, and have very long wings giving low flight power and cost of transport, and unusually long, rounded tips for control and stability in flight. Carnivores must carry heavy loads, and thus have relatively large wing areas; their foraging strategies consist of perching, hunting and gleaning, and wing structure is similar to that of insectivorous species with similar behaviour. Perching and hovering nectarivores both have a relatively small wing area: this surprising result may result from environmental pressure for a short wingspan or from the advantage of high speed during commuting flights; the large wingtips of these bats are valuable for lift generation in slow flight. The relation between flight morphology (as an indicator of flight behaviour) and echolocation is considered. It is demonstrated that adaptive trends in wing adaptations are predictably and closely paralleled by echolocation call structure, owing to the joint constraints of flying and locating food in different ways. Pressures on flight morphology depend also on size, with most aspects of performance favouring smaller animals. Power rises rapidly as mass increases; in smaller bats the available energy margin is greater than in larger species, and they may have a more generalized repertoire of flight behaviour. Trophic pressures related to feeding strategy and behaviour are also important, and may restrict the size ranges of different feeding classes: insectivores and primary nectarivores must be relatively small, carnivores and frugivores somewhat larger. The relation of these results to bat community ecology is considered, as our predictions may be tested through comparisons between comparable, sympatric species. Our mechanical predictions apply to all bats and to all kinds of bat communities, but other factors (for example echolocation) may also contribute to specialization in feeding or behaviour, and species separation may not be determined solely by wing morphology or flight behaviour. None the less, we believe that our approach, of identifying functional correlates of bat flight behaviour and identifying these with morphological adaptations, clarifies the eco-morphological relationships of bats.
Seed and fruit size are important to rain forest trees because they limit what can disperse their seeds and they influence what type of defenses and nutrient reserves their seedlings will acquire, Where establishment conditions might favor larger seeds, maximum seed size can be constrained by disperser size. Because the Paleotropics have larger frugivores than the Neotropics, I predicted more large fruits would be found in the Paleotropics. In eight pantropicai, endozoochorous plant families, the Old World representatives tended to have more taxa with larger fruits than the New World representatives. In all families the mean and range of fruit sizes were greater in the Old World, which suggests that the evolution of large fruits and seeds might be more tightly constrained in the Neotropics owing to the relative scarcity of large frugivores there.
Prey detection by echolocation limits the maximum size of aerial insectivorous bats. One drawback of this system of prey detection is that bats typically detect insects only within a few meters due to the weakness of the echoes reflected from insects and the rapid atmospheric attenuation of high frequency sounds. The short detection range puts a premium on maneuverability for aerial insectivorous bats, and this in itself could restrict their size. The authors' hypothesis is that, contrary to other predators, the prey available to large aerial insectivorous bats is restricted to large prey. Because large insects are relatively rare, aerial insectivorous bats are small because the prey detection system these bats use limits the availability of insects and makes the existence of large species energetically impossible. The flutter-detecting echolocation system used by rhinolophid, hipposiderid and mormoopid bats may be an alternative solution to the prey detection range problem that has allowed these bats to use high-frequency sounds and evolve larger sizes than other aerial insectivorous bats. -from Authors
Strict and semi-strict supertree construction methods can be used to summarize groups that are consistent with all source phylogenies. Other procedures, such as Matrix Representation with Parsimony (MRP), arbitrate conflicts among incompatible source trees, and can provide more topological resolution than strict and semi-strict methods. MRP has been used to construct most of the large supertrees that have been published to date. We review some of the inherent problems with MRP and other supertree methods, point out specific difficulties in previously published MRP-supertree analyses, question some of the possible advantages of supertrees, and suggest that supermatrix analyses of character data should provide the primary framework for comparative biology in the 21st century.
Andersen's 1912 monograph on megachiropterans remains the definitive work on the systematics of this group. Andersen argued that the Macroglossinae, containing the eonycterine and notopterine sections, are a monophyletic sister-group to other fruitbats (i.e. Andersen's Rousettus, Cynopterus and Epomophorus sections). Two recent molecular studies (DNA hybridisation and restriction mapping of ribosomal cistrons), as well as an analysis of female reproductive characters, challenge the monophyly of the Macroglossinae and several of Andersen's other conclusions such as the phylogenetic position of Nyctimene. We performed a cladistic analysis on 36 morphological characters, including 33 that were gleaned from Andersen, to determine whether phylogenetic hypotheses based on modem phylogenetic methods are in agreement with Andersen's original conclusions and to compare morphological and molecular phylogenetic hypotheses. Minimum-length trees based on parsimony are largely consistent with Andersen and support (1) a monophyletic Macroglossinae, within which the eonycterine section is paraphyletic with respect to a monophyletic notopterine section, (2) a monophyletic Cynopterus section, excepting the exclusion of Myonycteris, (3) a monophyletic Epomophorus section, excepting the exclusion of Plerotes, and (4) a paraphyletic Rousettus section, with several of the Rousettus-like forms branching off near the base of the tree. Bootstrapping analyses on a reduced data-set that included taxa shared in common with the DNA hybridisation study did not provide strong support (2 95%) for any clades but didprovide moderate support (2 70) for several clades, including a monophyletic Macroglossinae. These findings are in marked contrast to the DNA hybridisation phylogeny. A high index of between-data-set incongruence is further evidence for the clash between DNA hybridisation and morphology. A phylogenetic framework was constructed on the basis of morphological data and DNA hybridisation data using a criterion of moderate support and shows little resolution, whereas employing a criterion of strong support produced a framework resolving several additional nodes. One implication of this framework is that characteristic macroglossine features such as a long tongue with a thick carpet of filiform papillae have evolved independently on several occasions (or evolved once and were lost several times). Rates of character evolution for the morphological characters employed in our analysis were calculated using divergence times estimated from DNA hybridisation data. Rates have apparently been fastest in the interior branches, and slower along the external branches, which suggests an early adaptive radiation in the history of fruitbats.
We constructed DNA-hybridisation matrices comparing 18 genera of Megachiroptera and an outgroup microchiropteran, and eight species of Pteropus and two related genera. Three species each of Megachiroptera and Microchiroptera, two of Primates, and an outgroup armadillo were compared in another matrix; additional representatives of other mammalian orders figured in a further set of experiments. Among the megachiropterans examined, Nyctimene and Paranyctimene comprise the sister-group to other pteropodids. Of the 'macroglossines', only Macroglossus and Syconycteris are associated apart from typical pteropodines, while the four remaining nectar-feeders (Eonycteris, Megaloglossus, Melonycteris, Notopteris) are independently linked with non-nectar-feeding clades. Thus, Megaloglossus is the nearest relative of Lissonycteris, with Epomophorus and Rousettus successive sister-groups to both, while Eonycteris is the sister of all four; Melonycteris and Pteralopex form a trichotomy with the closely related Acerodon and Pteropus, and Notopteris is the sister-taxon to all four. It therefore appears that anatomical specialisations for nectar-and pollen-feeding evolved (or were lost) several times within Pteropodidae. Cynopterus and Dobsonia represent additional clades within the Pteropodinae, with which Thoopterus and Aproteles are respectively paired. Comparisons among species of Pteropus and related genera suggest that Acerodon may be congeneric with Pteropus, but that Pteralopex clearly is not. The ordinal-level matrices support bat monophyly: no order tested is closer to either of the chiropteran suborders than they are to each other, and bats are separated from Primates by at least two nodes. On the basis of previous rate determinations for mammals, we estimate that the African grouping (Epomophorus, Megaloglossus, Lissonycteris) is mid-Miocene in origin, that the two major pteropodid subfamilies (Nyctimeninae and Pteropodinae, including 'Macroglossinae') separated in the Early Miocene, and that the divergence of chiropteran suborders dates from the latest Cretaceous or earliest Palaeocene. Arrangement of genera within Pteropodidae supports the family's Australo-Pacific or south-east Asian origin.
We constructed DNA-hybridisation matrices comparing 18 genera of Megachiroptera and an outgroup microchiropteran, and eight species of Pteropus and two related genera. Three species each of Megachiroptera and Microchiroptera, two of Primates, and an outgroup armadillo were compared in another matrix; additional representatives of other mammalian orders figured in a further set of experiments. Among the megachiropterans examined, Nyctimene and Paranyctimene comprise the sister-group to other pteropodids. Of the 'macroglossines', only Macroglossus and Syconycteris are associated apart from typical pteropodines, while the four remaining nectar-feeders (Eonycteris, Megaloglossus, Melonycteris, Notopteris) are independently linked with non-nectar-feeding clades. Thus, Megaloglossus is the nearest relative of Lissonycteris, with Epomophorus and Rousettus successive sister-groups to both, while Eonycteris is the sister of all four; Melonycteris and Pteralopex form a trichotomy with the closely related Acerodon and Pteropus, and Notopteris is the sister-taxon to all four. It therefore appears that anatomical specialisations for nectar-and pollen-feeding evolved (or were lost) several times within Pteropodidae. Cynopterus and Dobsonia represent additional clades within the Pteropodinae, with which Thoopterus and Aproteles are respectively paired. Comparisons among species of Pteropus and related genera suggest that Acerodon may be congeneric with Pteropus, but that Pteralopex clearly is not. The ordinal-level matrices support bat monophyly: no order tested is closer to either of the chiropteran suborders than they are to each other, and bats are separated from Primates by at least two nodes. On the basis of previous rate determinations for mammals, we estimate that the African grouping (Epomophorus, Megaloglossus, Lissonycteris) is mid-Miocene in origin, that the two major pteropodid subfamilies (Nyctimeninae and Pteropodinae, including 'Macroglossinae') separated in the Early Miocene, and that the divergence of chiropteran suborders dates from the latest Cretaceous or earliest Palaeocene. Arrangement of genera within Pteropodidae supports the family's Australo-Pacific or south-east Asian origin.
Molecular and morphological data have important roles in
illuminating evolutionary history. DNA data often yield well resolved
phylogenies for living taxa, but are generally unattainable for
fossils. A distinct advantage of morphology is that some types of
morphological data may be collected for extinct and extant taxa.
Fossils provide a unique window on evolutionary history and may
preserve combinations of primitive and derived characters that are not
found in extant taxa. Given their unique character complexes, fossils
are critical in documenting sequences of character transformation over
geologic time and may elucidate otherwise ambiguous patterns of
evolution that are not revealed by molecular data alone. Here, we
employ a methodological approach that allows for the integration of
molecular and paleontological data in deciphering one of the most
innovative features in the evolutionary history of mammals—laryngeal
echolocation in bats. Molecular data alone, including an expanded data
set that includes new sequences for the A2AB gene, suggest that
microbats are paraphyletic but do not resolve whether laryngeal
echolocation evolved independently in different microbat lineages or
evolved in the common ancestor of bats and was subsequently lost in
megabats. When scaffolds from molecular phylogenies are incorporated
into parsimony analyses of morphological characters, including
morphological characters for the Eocene taxa
Icaronycteris, Archaeonycteris,
Hassianycteris, and Palaeochiropteryx,
the resulting trees suggest that laryngeal echolocation evolved in the
common ancestor of fossil and extant bats and was subsequently lost in
megabats. Molecular dating suggests that crown-group bats last shared a
common ancestor 52 to 54 million years ago.
Bats (order Chiroptera) are one of the few orders of mammals that echolocate and the only group with the capacity for powered flight. The order is subdivided into Microchiroptera and Megachiroptera, with an array of characteristics defining each group, including complex laryngeal echolocation systems in microbats and enhanced visual acuity in megabats. The respective monophylies of the two suborders have been tacitly assumed, although microbat monophyly is uncorroborated by molecular data. Here we present a phylogenetic analysis of bat relationships using DNA sequence data from four nuclear genes and three mitochondrial genes (total of 8,230 base pairs), indicating that microbat families in the superfamily Rhinolophoidea are more closely related to megabats than they are to other microbats. This implies that echolocation systems either evolved independently in rhinolophoids and other microbats or were lost in the evolution of megabats. Our data also reject flying lemur (order Dermoptera) as the bat sister group, indicating that presumed shared derived characters for flying lemurs and bats are convergent features that evolved in association with gliding and flight, respectively.
Phyllostomidae is a large (> 140 species), diverse clade of Neotropical bats. Different species in this family feed on blood, insects, vertebrates, nectar, pollen, and fruits. We investigated phylogenetic relationships among all genera of phyllostomid bats and tested monophyly of several genera (e.g., Micronycteris, Mimon, Artibeus, Vampyressa) using 150 morphological, karyological, and molecular characters. Results of parsimony analyses of these combined data indicate that all traditionally recognized phyllostomid subfamilies are monophyletic and that most taxa that share feeding specializations form clades. These results largely agree with studies that have used a taxonomic congruence approach to evaluate karyological, immunological, and limited sets of morphological characters, although our finding that Phyllostominae is monophyletic is novel. Our results indicate that several genera (Micronycteris, Artibeus, and Vampyressa) are not monophyletic. We propose a new classification for Phyllostomidae that better reflects hypothesized evolutionary relationships. Important features of this new classification include: (1) formal recognition of two clades that group nectarivorous and frugivorous subfamilies, respectively, (2) redefinition of Glossophaginae and recognition of two tribal-level taxa within that subfamily, (3) recognition of several tribal-level taxa in Phyllostominae, (4) formal recognition of two clades that have been colloquially referred to as “short-faced” and “long-faced” stenodermatines, (5) elevation of the subgenera of Micronycteris to generic rank, (6) recognition of Mesophylla as a junior synonym of Ectophylla, (7) recognition of Enchisthenes as a distinct genus, and (8) retention of Dermanura and Koopmania as subgenera of Artibeus. Although Vampyressa is not monophyletic in our tree, we recommend no nomenclatural change because we did not include all Vampyressa species in our study. Comparisons of character and taxonomic congruence approaches indicate that character congruence provides improved resolution of relationships among phyllostomids. Many data sets are informative only at limited hierarchical levels or in certain portions of the phyllostomid tree. Although both chromosomal and immunological data provide additional support for several clades that we identified, these data sets are incongruent with many aspects of our phylogenetic results. These conflicts may be due to methodological constraints associated with the use of karyological and immunological data (e.g., problems with assessing homologies and distinguishing primitive from derived traits). Among other observations, we find that Macrotus waterhousii, which has been thought to have the primitive karyotype for the family, nests well within the phyllostomine clade. This suggests that results of previous analyses of chromosomal data may need to be reevaluated. Mapping characters and behaviors on our phylogenetic tree provides a context for evaluating hypotheses of evolution in Phyllostomidae. Although previous studies of uterine evolution in phyllostomids and other mammals have generally supported the unidirectional progressive fusion hypothesis, our results indicate that intermediate stages of external uterine fusion are often derived relative to the fully simplex condition, and that reversals also occur with respect to internal uterine fusion. Uterine fusion therefore appears to be neither completely unidirectional nor progressive in Phyllostomidae. Evolution of the vibrissae and noseleaf is similarly complex and homoplasy is common in these structures; however, many transformations in these systems diagnose clades of phyllostomids. Within Phyllostomidae, there is considerable derived reduction in numbers of vibrissae present in various vibrissal clusters. The phyllostomid noseleaf seems to have become a much more elaborate and complex structure over evolutionary time. Primitively within the family, the spear was short, the internarial region was flat, and the horseshoe was undifferentiated from the upper lip. Subsequently, within the various subfamilies, the spear became more elongate, the central rib and other internarial structures evolved, and the labial horseshoe became flaplike or cupped in some taxa. Dietary evolution in phyllostomids appears somewhat more complex than previously thought. We find that most of the major dietary guilds (e.g., frugivory, sanguivory) are represented by a single large clade within Phyllostomidae, indicating that each feeding specialization evolved once. However, reversals do occur (e.g., loss of nectar- and pollen-feeding in many phyllostomines and stenodermatines), and some specializations may have evolved more than once (e.g., carnivory).
Supertree construction is a new, rigorous approach for combining phy-logenetic information to produce more inclusive phylogenies. It has been used to pro-vide some of the largest, most complete phylogenies for diverse groups (e.g., mammals, flowering plants, and dinosaurs) at a variety of taxonomic levels. We critically review methods for assembling supertrees, discuss some of their more interesting mathemat-ical properties, and describe the strengths and limitations of the supertree approach. To document the need for supertrees in biology, we identify how supertrees have al-ready been used beyond the systematic information they provide to examine models of evolution, test rates of cladogenesis, detect patterns of trait evolution, and extend phylogenetic information to biodiversity conservation.
Abstract Before the Evolutionary Synthesis, ‘phylogenetic inertia’ was associated with theories of orthogenesis, which claimed that organisms possessed an endogenous perfecting principle. The concept in the modern literature dates to Simpson (1944), who used ‘evolutionary inertia’ as a description of pattern in the fossil record. Wilson (1975) used ‘phylogenetic inertia’ to describe population-level or organismal properties that can affect the course of evolution in response to selection. Many current authors now view phylogenetic inertia as an alternative hypothesis to adaptation by natural selection when attempting to explain interspecific variation, covariation or lack thereof in phenotypic traits. Some phylogenetic comparative methods have been claimed to allow quantification and testing of phylogenetic inertia. Although some existing methods do allow valid tests of whether related species tend to resemble each other, which we term ‘phylogenetic signal’, this is simply pattern recognition and does not imply any underlying process. Moreover, comparative data sets generally do not include information that would allow rigorous inferences concerning causal processes underlying such patterns. The concept of phylogenetic inertia needs to be defined and studied with as much care as ‘adaptation’.
We studied the echolocation and foraging behavior of two Neotropical frugivorous leaf-nosed bats (Carollia perspicillata, C. castanea: Phyllostomidae) in a flight cage. To test which cues Carollia uses to detect, identify, and localize ripe Piper fruit, their preferred natural food, we conducted experiments under semi-natural conditions with ripe, unripe, and artifical
fruits. We first offered the bats ripe fruits and documented their foraging behavior using multiflash stereophotography combined
with simultaneous sound recordings. Both species showed a similar, stereotyped foraging pattern. In searchflight, the bats circled through the flight cage in search of a branch with ripe fruit. After finding such a branch, the bats switched
to approach behavior, consisting of multiple exploration flights and the final approach when the bats picked up the fruit at its tip and tore it off in flight. Our behavioral experiments revealed that odor plays
an important role in enabling Carollia to find ripe fruit. While foraging, Carollia always echolocated and produced multiharmonic, frequency-modulated (FM) signals of broad bandwidth, high frequency, short
duration, and low intensity. We discriminated an orientation phase (mostly a single pulse per wingbeat) and an approach phase (groups of two to six pulses per wing beat). We conclude from the bats' behavioral reaction to real and artificial fruit
as well as from characteristic patterns in their echolocation behavior that during exploration flights, Carollia changes from primarily odor-oriented detection and initial localization of ripe fruit to a primarily echo-oriented final
localization of the position of the fruit.
We present the first estimate of the phylogenetic relationships among all 916 extant and nine recently extinct species of bats (Mammalia:Chiroptera), a group that accounts for almost one-quarter of extant mammalian diversity. This phylogeny was derived by combining 105 estimates of bat phylogenetic relationships published since 1970 using the supertree construction technique of Matrix Representation with Parsimony (MRP). Despite the explosive growth in the number of phylogenetic studies of bats since 1990, phylogenetic relationships in the order have been studied non-randomly. For example, over one-third of all bat systematic studies to date have focused on relationship within Phyllostomidae, whereas relationships within clades such as Kerivoulinae and Murinae have never been studied using cladistic methods. Resolution in the supertree similarly differs among clades: overall resolution is poor (46.4% of a fully bifurcating solution) but reaches 100% in some groups (e.g. relationships within Mormoopidae
The Eocene fossil record of bats (Chiroptera) includes four genera known from relatively complete skeletons: lcaronycteris, Archaeonycteris, Hassianycteris, and Palaeochiropteryx. Phylogenetic relationships of these taxa to each other and to extant lineages of bats were investigated in a parsimony analysis of 195 morphological characters, 12 rDNA restriction site characters, and one character based on the number of R-1 tandem repeats in the mtDNA d-loop region. Results indicate that lcaronycteris, Archaeonycteris, Hassianycteris, and Palaeochiropteryx represent a series of consecutive sister-taxa to extant microchiropteran bats. This conclusion stands in contrast to previous suggestions that these fossil forms represent either a primitive grade ancestral to both Megachiroptera and Microchiroptera (e.g., Eochiroptera) or a separate clade within Microchiroptera (e.g., Palaeochiropterygoidea). A new higher-level classification is proposed to better reflect hypothesized relationships among Eocene fossil bats and extant taxa. Critical features of this classification include restriction of Microchiroptera to the smallest clade that includes all extant bats that use sophisticated echolocation (Emballonuridae + Yinochiroptera + Yangochiroptera), and formal recognition of two more inclusive clades that encompass Microchiroptera plus the four fossil genera. Comparisons of results of separate phylogenetic analyses including and subsequently excluding the fossil taxa indicate that inclusion of the fossils changes the results in two ways: (1) altering perceived relationships among extant forms at a few poorly supported nodes; and (2) reducing perceived support for some nodes near the base of the tree. Inclusion of the fossils affects some character polarities (hence slightly changing tree topology), and also changes the levels at which transformations appear to apply (hence altering perceived support for some clades). Results of an additional phylogenetic analysis in which soft-tissue and molecular characters were excluded from consideration indicate that these characters are critical for determination of relationships among extant lineages. Our phytogeny provides a basis for evaluating previous hypotheses on the evolution of flight, echolocation, and foraging strategies. We propose that flight evolved before echolocation, and that the first bats used vision for orientation in their arboreal/aerial environment. The evolution of flight was followed by the origin of low-duty-cycle laryngeal echolocation in early members of the microchiropteran lineage. This system was most likely simple at first, permitting orientation and obstacle detection but not detection or tracking of airborne prey. Owing to the mechanical coupling of ventilation and flight, the energy costs of echolocation to flying bats were relatively low. In contrast, the benefits of aerial insectivory were substantial, and a more sophisticated low-duty-cycle echolocation system capable of detecting, tracking, and assessing airborne prey subsequently evolved rapidly. The need for an increasingly derived auditory system, together with limits on body size imposed by the mechanics of flight, echolocation, and prey capture, may have resulted in reduction and simplification of the visual system as echolocation became increasingly important. Our analysis confirms previous suggestions that Icaronycteris, Archaeonycteris, Hassianycteris, and Palaeochiropteryx used echolocation. Foraging strategies of these forms were reconstructed based on postcranial osteology and wing form, cochlear size, and stomach contents. In the context of our phylogeny, we suggest that foraging behavior in the microchiropteran lineage evolved in a series of steps: (1) gleaning food objects during short flights from a perch using vision for orientation and obstacle detection; prey detection by passive means, including vision and/or listening for prey-generated sounds (no known examples in fossil record); (2) gleaning stationary prey from a perch using echolocation and vision for orientation and obstacle detection; prey detection by passive means (Icaronycteris, Archaeonycteris); (3) perch hunting for both stationary and flying prey using echolocation and vision for orientation and obstacle detection; prey detection and tracking using echolocation for flying prey and passive means for stationary prey (no known example, although Icaronycteris and/or Archaeonycteris may have done this at times); (4) combined perch hunting and continuous aerial hawking using echolocation and vision for orientation and obstacle detection; prey detection and tracking using echolocation for flying prey and passive means for stationary prey; calcar-supported uropatagium used for prey capture (common ancestor of Hassianycteris and Palaeochiropteryx; retained in Palaeochiropteryx); (5) exclusive reliance on continuous aerial hawking using echolocation and vision for orientation and obstacle detection; prey detection and tracking using echolocation (Hassianycteris; common ancestor of Microchiroptera). The transition to using echolocation to detect and track prey would have been difficult in cluttered envionments owing to interference produced by multiple returning echoes. We therefore propose that this transition occurred in bats that foraged in forest gaps and along the edges of lakes and rivers in situations where potential perch sites were adjacent to relatively clutter-free open spaces. Aerial hawking using echolocation to detect, track, and evalute prey was apparently the primitive foraging strategy for Microchiroptera. This implies that gleaning, passive prey detection, and perch hunting among extant microchiropterans are secondarily derived specializations rather than retentions of primitive habits. Each of these habits has apparently evolved multiple times. The evolution of continuous aerial hawking may have been the "key innovation" responsible for the burst of diversification in microchiropteran bats that occurred during the Eocene. Fossils referable to six major extant lineages are known from Middle-Late Eocene deposits, and reconstruction of ghost lineages leads to the conclusion that at least seven more extant lineages were minimally present by the end of the Eocene.
1. It has been proposed that echolocating bats normally emit one call per wingbeat when searching for prey. The coupling of sound production with flapping makes the production of intense sound pulses cost no more in energetic terms than beating the wings and not calling, whereas calling without flapping would be energetically expensive. The scaling of wingbeat frequency and pulse repetition rate with body mass was investigated in a cross-species analysis to test the hypothesis that calling and flapping are coupled in echolocating bats. 2. For 57 species where measurements of pulse repetition rate were available, most bats (75%) emitted 0.5-2 pulses per predicted wingbeat during search phase. In some fast-flying bats (12% of sample), fewer than the predicted one pulse per beat were produced, perhaps because such bats skipped calling during some wingbeats, or possibly because wingbeat frequencies were very slow when the bats were cruising in open habitats. A few species (12%) appeared to produce several pulses per wingbeat. Such species were gleaners, and often produced low-intensity calls. For bats which emitted intense calls and foraged largely by aerial hawking, pulse repetition rate scaled as body mass (M)-0.775. In echolocating bats, wingbeat frequency scaled as M-0.326. 3. Aerial feeding bats typically emit intense search phase calls, and it is concluded that such bats normally produce one or fewer pulses per wingbeat during search phase, as predicted by the coupling hypothesis. Coupling may constrain maximal body size in aerial insectivorous bats because very large bats may be unable to echolocate at a sufficiently high rate to catch enough insects to meet the high energetic demands associated with large size. Some bats may be able to trade-off call intensity against repetition rate, however, and produce several low-intensity pulses per wingbeat. These bats were usually gleaners. Bats in the family Hipposideridae appear to have specialized echolocation which allows the production of several high-intensity calls per wingbeat.
We carried out DNA-hybridization comparisons among representatives of the major groups of Chiroptera to determine the phylogenetic position of the New Zealand short-tailed bat, Mystacina tuberculata. All analyses confirmed the noctilionoid affinity of this species suggested by an earlier serological study, with support from taxon jackknifing and at bootstrap levels of 98% or higher. However, a specific association with Noctilio was not found in more than 13% of the bootstrapped trees. The most precise of the thermal-stability indices employed (Tm, the median melting temperature of hybridized sequences) demonstrated a sister-group relationship of Mystacina to all noctilionoids, with Noctilio the first branch within Noctilionoidea but separated from the Mystacina lineage by a very short internode. Our determination of the timing of the divergence of Mystacina from noctilionoids is 54 myrbp. This estimate is based on independent indications that extant bat lineages began to diversify in the latest Cretaceous and is much earlier than the tentative estimate of 35 myrbp inferred from serology. Even if the diversification of all living bats occurred as early as 83 myrbp, as some authors have suggested, separation of Mystacinidae—on that basis, at 66 myrbp—could not have taken place soon enough for this taxon to be isolated on New Zealand before New Zealand separated from the rest of Gondwanaland. However, any of these dates would allow for the distribution of the noctilionoid–mystacinid common ancestor in South America, Australia, and Antarctica before the final sundering of Australia from Antarctica and for the divergence of Mystacinidae as a possible result of that event. This hypothesis is supported by the presence of fossil mystacinids in early and mid-Miocene deposits at Bullock Creek and Riversleigh, Queensland, showing that Mystacinidae had been resident in Australia from at least 25–20 myrbp. The most obvious scenario explaining the presence of Mystacinidae in New Zealand is therefore fortuitous dispersal from Australia across the Tasman Sea.
Parallel or convergent morphological evolution can be demonstrated either by comparisons of the size and shape of birds in different lineages that occupy the same micro-habitat or by comparisons of taxa that occupy similar but distant environments. The common notion that interspecific constraints affect adaptive radiation in a lineage is probably incorrect because it rests on unsupported evidence of character displacement. At the generic level, wherein differences in morphology between species can be judged against the standard of recent common ancestry, very small differences in the shape of the feeding, wing, and/or leg complexes may be correlated with species-specific differences in foraging behavior. Morphological relationships among species in communities are more difficult to interpret. Many purported regularities in the size ratios of coexisting species cannot be distinguished from randomly distributed arrays of species sizes. Recently developed methods of size and shape analysis, and the possibility of field experiments designed to estimate the genetic and nongenetic components of the observed morphological variation, will probably permit new insights into the mechanisms underlying the morphological differentiation of birds.-from Author
The purpose of my study is to examine as many species of the family Molossidae as possible and to determine, with the aid of numerical methods, what natural groups exist within the family. Sneath & Sokal (1973) discuss the methods and reasons for this kind of analysis. A natural group of organisms as here defined is one in which its members share a close phenetic relationship. Phenetic relationship is defined as "similarity (resemblance) based on a set of phenotypic characteristics of the objects or organisms under study," (Sneath & Sokal, 1973, p. 29), and is distinct in definition from phylogenetic relationship. However, I have used phenetic relationships to help estimate phylogenetic ones. I think that the estimation of the evolutionary relationships from phenetics is best observed when size of the organism is not a factor, and for this reason, I place much emphasis on the shape analyses in my study (for a discussion, see Sneath & Sokal, 1973, pp. 168-178). Analysis with size included can be very important in the estimation of ecological relationships. A natural group of bats in the family Molossidae includes individuals of a certain shape category and can be distinguished from individuals of a different shape category. I think each shape category or group indicates a certain way of life. Often, these natural shape groups correspond with classical genera or subgenera and are described in terms of those taxonomic names. Here, I examine the family Molossidae phenetically, determine how many natural shape groups have evolved within it, predict the resulting diverse ways of life, and estimate the evolutionary relationships among the species and groups. A few of the characters can be graded as to their primitive-derived nature and accompany the evolution discussion. The analyses used were designed not so much to distinguish one species from another, but to detect underlying morphological trends. Document = viii + 173 pages. Includes 25 figures, 12 tables, summary of names, key to genera and subgenera, and bibliography.
Results of recent molecular studies cast doubt on the validity of the superorder Archonta, suborders Megachiroptera and Microchiroptera, and infraorder Yinochiroptera and has even led some to consider novel alternatives for the evolution of flight and echolocation in mammals. At present, higher-level relationships within Chiroptera still is without consensus, and much of this controversy is related to how bats are related to other mammals and also to relationships among family-level lineages within Chiroptera. Although this controversy superficially manifests itself as differences in the relative merits of morphologic versus molecular data, both classes of data are themselves conflicting. We contend that much of the discrepancy among these studies is due to improper choice of out-group, limited taxonomic sampling, or both. We examined approximately 3 kb of mitochondrial DNA from 104 bats representing the taxonomic, geographic, and morphologic diversity within all families (except the monotypic Craseonycteridae) and 58 additional taxa representing 12 other orders of mammals. Results of our analyses strongly support other recent work indicating that Archonta is not a natural assemblage and that the sister taxon to Chiroptera may include Cetartiodactyla, Perissodactyla, Carnivora, and possibly Pholidota. Using representatives of these taxa as out-groups to evaluate interfamilial relationships within Chiroptera, we detected strong support for recognition of the suborders Yinpterochiroptera and Yangochiroptera. Within Yangochiroptera, our analyses strongly support expansion of the superfamily Noctilionoidea to include the New World Thyropteridae and Furipteridae.
Andersen's 1912 monograph on megachiropterans remains the definitive work on the systematics of this group. Andersen argued that the Macroglossinae, containing the eonycterine and notopterine sections, are a monophyletic sister-group to other fruitbats (i.e. Andersen's Rousettus, Cynopterus and Epomophorus sections). Two recent molecular studies (DNA hybridisation and restriction mapping of ribosomal cistrons), as well as an analysis of female reproductive characters, challenge the monophyly of the Macroglossinae and several of Andersen's other conclusions such as the phylogenetic position of Nyctimene. We performed a cladistic analysis on 36 morphological characters, including 33 that were gleaned from Andersen, to determine whether phylogenetic hypotheses based on modem phylogenetic methods are in agreement with Andersen's original conclusions and to compare morphological and molecular phylogenetic hypotheses. Minimum-length trees based on parsimony are largely consistent with Andersen and support (1) a monophyletic Macroglossinae, within which the eonycterine section is paraphyletic with respect to a monophyletic notopterine section, (2) a monophyletic Cynopterus section, excepting the exclusion of Myonycteris, (3) a monophyletic Epomophorus section, excepting the exclusion of Plerotes, and (4) a paraphyletic Rousettus section, with several of the Rousettus-like forms branching off near the base of the tree. Bootstrapping analyses on a reduced data-set that included taxa shared in common with the DNA hybridisation study did not provide strong support (greater than or equal to 95%) for any clades but did provide moderate support (greater than or equal to 70) for several clades, including a monophyletic Macroglossinae. These findings are in marked contrast to the DNA hybridisation phylogeny. A high index of between-data-set incongruence is further evidence for the clash between DNA hybridisation and morphology. A phylogenetic framework was constructed on the basis of morphological data and DNA hybridisation data using a criterion of moderate support and shows little resolution, whereas employing a criterion of strong support produced a framework resolving several additional nodes. One implication of this framework is that characteristic macroglossine features such as a long tongue with a thick carpet of filiform papillae have evolved independently on several occasions (or evolved once and were lost several times). Rates of character evolution for the morphological characters employed in our analysis were calculated using divergence times estimated from DNA hybridisation data. Rates have apparently been fastest in the interior branches, and slower along the external branches, which suggests an early adaptive radiation in the history of fruitbats.
Theories of ecological diversification make predictions about the timing and ordering of character state changes through history. These theories are testable by "reconstructing" ancestor states using phylogenetic trees and measurements of contemporary species. Here we use maximum likelihood to estimate and evaluate the accuracy of ancestor reconstructions. We present likelihoods of discrete ancestor states and derive probability distributions for continuous ancestral traits. The methods are applied to several examples: diets of ancestral Darwin's finches; origin of inquilinism in gall wasps; microhabitat partitioning and body size evolution in scrubwrens; digestive enzyme evolution in artiodactyl mammals; origin of a sexually selected male trait, the sword, in platies and swordtails; and evolution of specialization in Anolis lizards. When changes between discrete character states are rare, the maximum likelihood results are similar to parsimony estimates. In this case the accuracy of estimates is often high, with the exception of some nodes deep in the tree. If change is frequent then reconstructions are highly uncertain, especially of distant ancestors. Ancestor states for continuous traits are typically highly uncertain. We conclude that measures of uncertainty are useful and should always be provided, despite simplistic assumptions about the probabilistic models that underlie them. If uncertainty is too high, reconstruction should be abandoned in favor of approaches that fit different models of trait evolution to species data and phylogenetic trees, taking into account the range of ancestor states permitted by the data.
Several hundred species of neotropical plants are pollinated by glossophagine bats¹,². These bats use their highly developed sonar system for orientation, so we might expect bat-pollinated flowers to have evolved acoustically conspicuous structures to make them easier to detect. We find that the bat-pollinated neotropical vine Mucuna holtonii directs its echolocating pollinators to its flowers by means of an acoustic nectar guide. The flower contains a small concave ‘mirror’ that works like an optical cat's eye, but in the acoustic domain, reflecting most of the energy of the bats' echolocation calls back into the direction of incidence.
The purpose of this chapter is to illustrate some ways in which data on the characteristics of Amniotes can be combined with phylogenic information. It also aims to develop analytical methods that draw inferences about the characteristics of hypothetical ancestral organisms. The phenotypic trait considered here in is plasma osmolarity. It covers the literature of osmorality data for a total of 172 vertebrate taxa, including representatives of all major extant lineages. Additional information on phylogenetic relationships is provided in order to obtain a better estimate of the ancestral value. There are certain ways to show how parsimony can be used to map or optimize a character onto hypothetical phylogenic tree and reconstructs values for hypothetical ancestral organisms. The first and simplest outcome of a parsimony analysis is estimate of where and how many times a particular character state originated in a phylogenetic tree. Estimation of where in a phylogenetic tree a character state first evolved can also allow one to predict which descendant lineages should have it. The origin and present roles of parsimony is analyzed in a systematic and comparative biology.
Old World phytophagous bats (Megachiroptera: Pteropodidae) number 173 species of which 79% are Asian and 21% African. Bats arose, presumably monophyletically, in the early Tertiary, the Megachiroptera soon diverging from the Microchiroptera. By the Cretaceous-Tertiary boundary the major groups of modern angiosperms were present, some of these probably being pollinated nocturnally by large insects and non-flying mammals and others with seeds dispersed by terrestrial vertebrates. Early bats were perhaps initially attracted to such flowers and fruit by the insects found around them, later finding the plants themselves nutritious. Megabats today feed upon floral resources, fruit and leaves from a total of at least 188 plant genera in 64 families. They may effect both pollination and seed-dispersal, and both bat-flower and bat-fruit syndromes are commonly recognized. Individual species are generally catholic in their feeding, favoured food varying with locality and season. Depending upon roosting habits and season, megabats may travel considerable distances each night to feed and may undertake seasonal migrations. Their feeding in orchards may sometimes require their control, but the future of certain species is more seriously threatened by slaughter for food and particularly by habitat destruction.
No family of mammals has undergone a greater adaptive radiation than phyllostomid bats. Phylogeny combined with eco-morphological considerations of trophic structures can help understand this adaptive radiation and the evolution of Microchiroptera. Microchiropteran bats are overwhelmingly insectivorous, and constraints within the morphospace of insectivory have produced a dynamic equilibrium in bat morphologies that has persisted for 60 million years. The ability to eat fruit may be the key synapomorphy that allowed phyllostomids to escape insectivore morphospace and diversify. Although many phyllostomids have changed greatly, others that have maintained insectivory have changed little, which is equally remarkable.
1. The relationship between plant morphology and the senses used by dispersal agents to find fruit was examined. ‘Flagellichory’ (fruit borne on pendulous structures), a costly morphology associated with dispersal by bats, is focused on.
2. Using Gurania spinulosa, a flagellichorous vine, and its major dispersal agent, Phyllostomus hastatus, the hypothesis was tested that flagellichory increases the conspicuousness of fruit to bats that use echolocation to find fruit.
3. The responses of wild-caught P. hastatus to various fruiting branch morphologies and fruit odour were recorded. Phyllostomus hastatus used echolocation rather than olfaction to detect fruit, and consistently chose fruit displayed on pendulous leafless branches, ignoring fruit held among leaves on horizontal branches.
4. By comparing echolocation signals with the distance between fruiting branches of G. spinulosa and surrounding vegetation, it was shown that pendulous fruiting branches present clear, clutter-free targets that can be detected by echolocating bats. This is the first demonstration of neotropical frugivorous bats using echolocation to find fruit.
We analyze, with an augmented data base, patterns of covariation of the three primary demographic parameters (age at maturity, fecundity, adult survival, all measured in the same unit of time) in lizards. This also constitutes a first attempt to use all three of these parameters for this group of species. We attempt to place these analyses in the framework of recent theories on life history evolution (Ferrière and Clobert, 1992; Charnov, 1993). Life history data were collected from the literature and from our original work, and a composite phylogeny was assembled, based on a variety of published sources. Using a phylogenetically based statistical method (independent contrasts), the allometric (log-log) relationship of fecundity (and of clutch size) in relation to snout-vent length was found to differ significantly between the two major clades of extant lizards, Iguania (43 species in our data set) and Scleroglossa (47 species). We therefore emphasize analyses done separately for the two clades. Without removing correlations with body size, the relationships between fecundity and survival, and between fecundity and age at maturity, were also found to differ between clades, which differs from Charnov's (1993) predictions. When correlations with body size were removed statistically, however, the two clades did not differ significantly in these relationships. In a principal components analysis (PCA) of the three demographic variables plus snout-vent length, the first axis explained the majority (53–57%) of variation in both clades, while the second axis explained 27–31% of the variation and loaded mainly on fecundity. In a PCA of size-adjusted demographic variables residuals (from log-log regressions on snout-vent length), the first axis explained 66–68% of the variation and was clearly interpretable as the classical “slow-fast” continuum, which has been described in birds and mammals. The PCA of residuals did not provide clear evidence of additional significant patterns of covariation. However, the rate of evolution of mortality (size-corrected), but not of fecundity or age at maturity, differed significantly between clades. Furthermore, fecundity and age at maturity, both corrected for variation in adult mortality (in addition to body size), were still significantly related, indicating the existence of other patterns of variation in these life history traits. In other words, the ratios between age at maturity and adult mortality, or between fecundity and adult mortality, were not found to be invariant, because the variation not accounted for by these ratios was significantly associated with variation in another variable. This result contradicts the prediction of Charnov (1993), and suggests the existence of other directions of evolution in these life history traits.
Abstract Studies of deep-sea biodiversity focus almost exclusively on geographic patterns of a-diversity. Few include the morphological or ecological properties of species that indicate their actual roles in community assembly. Here, we explore morphological disparity of shell architecture in gastropods from lower bathyal and abyssal environments of the western North Atlantic as a new dimension of deep-sea biodiversity. The lower bathyal-abyssal transition parallels a gradient of decreasing species diversity with depth and distance from land. Morphological disparity measures how the variety of body plans in a taxon fills a morphospace. We examine disparity in shell form by constructing both empirical (eigenshape analysis) and theoretical (Schindel's modification of Raup's model) morphospaces. The two approaches provide very consistent results. The centroids of lower bathyal and abyssal morphospaces are statistically indistinguishable. The absolute volumes of lower bathyal morphospaces exceed those of the abyss; however, when the volumes are standardized to a common number of species they are not significantly different. The abyssal morphospaces are simply more sparsely occupied. In terms of the variety of basic shell types, abyssal species show the same disparity values as random subsets of the lower bathyal fauna. Abyssal species possess no evident evolutionary innovation. There are, however, conspicuous changes in the relative abundance of shell forms between the two assemblages. The lower bathyal fauna contains a fairly equable mix of species abundances, trophic modes, and shell types. The abyssal group is numerically dominated by species that are deposit feeders with compact unsculptured shells.
We examined taxa from 13 of the 17 chiropteran families, using single-copy DNA hybridization. Five taxa that either represented points of controversy in systematics or were members of problematic families were included in the experiment. The resulting data were used to build phylogenetic trees of 14 and 19 taxa, and by combining this study's data with those from two previous studies, a supertree of 36 taxa was constructed. The trees based on the three different matrices are compared and contrasted, and a phylogenetic hypothesis supporting the association of the rhinolophoid and the pteropodid groups of bats is presented. On the basis of this study, we conclude that the phylogenetically correct placement of the family Nycteridae is in a clade that does not include their putative relatives, the Rhinolophoidea. Our results suggest that the Emballonuridae, while a monophyletic group, are well embedded within the Yangochiroptera, and do not comprise the sister taxon to all other microbats. This study supports earlier DNA-hybridization results with respect to the placement of Mystacinidae within the Noctilionoidea, replicating those earlier findings. Finally, we determine that Miniopterus may well warrant recognition as a family distinct from the Vespertilionidae in which it is usually placed.
Felsenstein (1985) developed a method for analyzing comparative data that calculates a set of mutually independent comparisons among the species. The method was designed to be used with phylogenies for which the true dichotomous branching pattern is known. However, available phylogenies often contain many incompletely resolved nodes, or nodes from which three or more branches emanate. This paper reports a generalization of Felsenstein's method that permits the analysis of incompletely resolved phylogenies. The method is general to any sort of phylogeny and, like Felsenstein's model can accommodate more than one model of evolutionary change. The method is implemented in a computer program which can make use of information on branch lengths, or, if branch length information is not available, an algorithm is used to calculate a set of branch lengths. The wider implications of the method are that it makes explicit the assumptions about unknown branching patterns and branch lengths that all comparative methods that are applied to incompletely resolved phylogenies must make.
Comparative studies of the relationship between 2 phenotypes, or between a phenotype and an environment, are frequently carried out by invalid statistical methods. Most regression, correlation, and contingency table methods, including nonparametric methods, assume that the points are drawn independently from a common distribution. When species are taken from a branching phylogeny, they are manifestly nonindependent. Use of a statistical method that assumes independence will cause overstatement of the significance in hypothesis tests. Some illustrative examples of these phenomena are given, and limitations of previous proposals of ways to correct for the nonindependence discussed. A method of correcting for the phylogeny is proposed. It requires that we know both the tree topology and the branch lengths, and that we be willing to allow the characters to be modeled by Brownian motion on a linear scale. Given these conditions, the phylogeny specifies a set of contrasts among species, contrasts that are statistically independent and can be used in regression or correlation studies. -from Author
From Darwin onward, it has been second nature for evolutionary biologists to think comparatively because comparisons establish the generality of evolutionary phenomena. Do large genomes slow down development? What lifestyles select for large brains? Are extinction rates related to body size? These are all questions for the comparative method, and this book is about how such questions can be answered.
The first chapter elaborates on suitable questions for the comparative approach and shows how it complements other approaches to problem-solving in evolution. The second chapter identifies the biological causes of similarity among closely related species for almost any observed character. The third chapter discusses methods for reconstructing phylogenetic trees and ancestral character states. The fourth chapter sets out to develop statistical tests that will determine whether different characters that exist in discrete states show evidence for correlated evolution. Chapter 5 turns to comparative analyses of continuously varying characters. Chapter 6 looks at allometry to exemplify the themes and methods discussed earlier, while the last chapter looks to future development of the comparative approach in both molecular and organismic biology.
Japanese translation (1997) The Comparative Method in Evolutionary Biology. Hokkaido University Press in cooperation with Oxford University Press.
Biologists often compare average phenotypes of groups of species defined cladistically or on behavioral, ecological, or physiological criteria (e.g., carnivores vs. herbivores, social vs. nonsocial species, endotherms vs. ectotherms). Hypothesis testing typically is accomplished via analysis of variance (ANOVA) or covariance (ANCOVA; often with body size as a covariate). Because of the hierarchical nature of phylogenetic descent, however, species may not represent statistically independent data points, degrees of freedom may be inflated, and significance levels derived from conventional tests cannot be trusted. As one solution to this degrees of freedom problem, we propose using empirically scaled computer simulation models of continuous traits evolving along “known” phylogenetic trees to obtain null distributions of F statistics for ANCOVA of comparative data sets. These empirical null distributions allow one to set critical values for hypothesis testing that account for nonindependence due to specified phylogenetic topology, branch lengths, and model of character change. Computer programs that perform simulations under a variety of evolutionary models (gradual and speciational Brownian motion, Ornstein-Uhlenbeck, punctuated equilibrium; starting values, trends, and limits to phenotypic evolution can also be specified) and that will analyze simulated data by ANCOVA are available from the authors on request. We apply the proposed procedures to the analysis of differences in homerange area between two clades of mammals, Carnivora and ungulates, that differ in diet. We also apply the phylogenetic autocorrelation approach and show how phylogenetically independent contrasts can be used to test for clade differences. All three phylogenetic analyses lead to the same surprising conclusion: for our sample of 49 species, members of the Carnivora do not have significantly larger home ranges than do ungulates. The power of such tests can be increased by sampling species so as to reduce the correlation between phylogeny and the independent variable (e.g., diet), thus increasing the number of independent evolutionary transitions available for study.
We examined the statistical performance (in terms of type I error rates) of Felsenstein's (1985, Am. Nat. 125:1–15) comparative method of phylogenetically independent contrasts for testing hypotheses about evolutionary correlations of continuous-valued characters. We simulated data along two different phylogenies, one for 15 species of plethodontid salamanders and the other for 49 species of Carnivora and ungulates. We implemented 15 different models of character evolution, 14 of which deviated from Brownian motion, which is in effect assumed by the method. The models studied included the Ornstein–Uhlenbeck process and punctuated equilibrium (change allowed in only one daughter at each bifurcation) both with and without trends and limits on how far phenotypes could evolve. As has been shown in several previous simulation studies, a nonphylogenetic Pearson correlation of species' mean values yielded inflated type I error rates under most models, including that of simple Brownian motion. Independent contrasts yielded acceptable type I error rates under Brownian motion (and in preliminary studies under slight deviations from this model), but they were inflated under most other models. This new result confirms the model dependence of independent contrasts. However, when branch lengths were checked and transformed, then type I error rates of independent contrasts were reduced. Moreover, the maximum observed type I error rates never exceeded twice the nominal P value at α = 0.05. In comparison, the nonphylogenetic correlation tended to yield extremely inflated (and highly variable) type I error rates. These results constitute another demonstration of the general superiority of phylogenetically based statistical methods over nonphylogenetic ones, even under extreme deviations from a Brownian motion model. These results also show the necessity of checking the assumptions of statistical comparative methods and indicate that diagnostic checks and remedial measures can substantially improve the performance of the independent contrasts method.