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Endemism: Origins and implications
Abstract and Figures
All taxa are endemic and occur in nested distributions at a range of spatial scales. Distinguishing endemics as either neoendemics or palaeoendemics may not be of practical value in analytical biogeography, but distinguishing extinction mediated endemics (cryptoendemics) from endemics which never had a significantly wider range (euendemics) would be useful for interpreting the history of geographic areas. Only cladistic phylogeny provides a tool for distinguishing these two types of endemic.
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... Although details in composition, timing and location will vary from site to site and region to region, the term will uniquely represent a cohesive type of refugium with a specific set of contemporary and historical factors that must be understood in order to finetune conservation efforts and potentially, to protect the many biotopes that are examples of this type of refugium and their delicate biocenoses. It also provides an example of how to address some of the issues revealed by workers who have published extensively about the terminological morass we must all wade through when reviewing the literature on the subject of biodiversity hot spots [4,[53][54][55][56][57][58][59] (see Appendix A). ...
... paleo-endemism) introduces investigator bias into the decision-making process [56] because the investigator must impose artificial boundaries on the limits of time and space under consideration. Another complication is that the clades we are studying would transition from one category to the other over the time interval we are considering for our narrative. ...
... Another complication is that the clades we are studying would transition from one category to the other over the time interval we are considering for our narrative. Fattorini [93] provides a detailed history of the endemism concept and some of the problems associated with the varied uses of paleo-and neoendemism while Myers et al. [56] proposed a detailed classification of different applications of endemism. However, we finally chose to avoid the use of these modifiers and will simply refer to our clades as endemics sensu Darwin's glossary entry [94], "peculiar to a given locality," with the qualifier "peculiar" distinguishing our use of the term from the way it is sometimes used to imply "indigenous to" or "native to." ...
The contemporary distribution of crenobiontic endemics in central Texas is enigmatic because only some springs are occupied by crenobionts despite other unoccupied springs having seemingly suitable habitats. In the absence of complete paleo-records, a cohesive and widely accepted explanation for this biogeography has eluded researchers for many years. We suggest that data on contemporary species with obligate coevolution, such as parasites with multiple obligate hosts in their life cycles, can help to fill intervening gaps in the paleo-record because the contemporary distribution of such a parasite indicates that its hosts cohabitated without interruption since the arrival of the parasite. To test this conjecture, we studied one such parasite endemic to a select few central Texas springs, Huffmanela huffmani. By studying the distribution of the intermediate host, geologic and paleo-climatic records, performing lab experiments with live animals, and examining archived museum specimens of the definitive hosts from the 1950s, we were able to test multiple predictions about how the distribution of H. huffmani became what it is today. Our results corroborate a narrative suggesting that several severe droughts since the Wisconsin glaciations are responsible for having sculpted the present-day distribution of central Texas crenobionts.
... Currently, there are eight valid species of Discias known from the Pacific, Atlantic and Indian Oceans (Bruce 1976;Kensley 1983;Boothe & Heard 1987;Fransen 1987;Myers & De Grave 2000;De Grave & Fransen 2011;Pachelle & De Grave 2015). However, only two species have been recorded from the northwest Pacific Ocean, namely Discias exul Kemp, 1920, recorded from the Ryukyu Islands (Nomura et al. 1996;Komai & Segonzac 2003;Pachelle & De Grave 2015), and Discias musicus Holthuis, 1981, originally described from the Mariana Islands (Holthuis 1981 Zoological Journal, 2022, 1088-1093Vol. ...
A new species of Disciadidae Rathbun, 1902, representing the first recorded observation of this caridean family from the South China Sea, is here described and illustrated from nearshore waters off Jinqing Island, in the Xisha Islands. The new species, Discias nanhaiensis sp. nov., is likely associated with a calcareous sponge species, Leucaltis sp. It is characterized by a lanceolate rostrum with serrated margins, a dorsomedial posterior tooth on the second pleomere, an unarticulated mandibular palp, non-serrate lateral margin of the uropodal exopod, and distal margin of telson with four pairs of spines, and these combined features may distinguish the new species from its congeners. An identification key to all Discias species is provided.
http://urn:lsid:zoobank.org:pub:0645B1F0-C9E4-4F30-8593-2C062CBC988B
... It is a species-trait indicator and was scored in five classes: holoendemic -species whose distribution is limited by ecological and physiological tolerance (score = 1); euryendemic -species with broad, more or less continuous or contiguous distribution, limited by biogeographical barriers (score = 2); stenoendemic -species with restricted, more or less continuous or contiguous distribution, limited by biogeographical barriers (score = 3); rhoendemic -species with widely disjunct distribution due to either vicariance or jump dispersal (score = 4); spot endemic (or microendemic) -species occurring in one locality only (score = 5) (Supplementary material Data 1). Scores were attributed following Myers and De Grave (2000) with a few adjustments allowing a better resolution of the degrees of endemicity observed in stygobitic species (Fattorini et al. 2020). Species constrained by geographical barriers were considered less able to cope with environmental changes as so requiring priority in conservation. ...
Biodiversity hotspots are routinely identified by grid‐based analyses, despite grids encompassing different habitats, thus hindering the potential to assess which habitat type accounts for the conservation priority assigned to a grid. In this study, we aimed at identifying the main hotspots for the conservation of the European stygobitic Crustacea Copepoda Harpacticoida at the groundwater habitat scale. A multi‐metric approach was used, based on six biodiversity indicators: species richness, endemicity, evolutionary origin, phylogenetic rarity, taxonomic distinctness, habitat specificity. The Hot Spot Analysis, based on the statistics Getis‐Ord Gi*, was used to compare the local to the global average values of each indicator to identify hotspots of conservation. The operational units used to perform the analyses were the groundwater habitat types, in order to gather all the possible patterns of spatial occupancy in terms of habitat variability. Eight biodiversity hotspots of stygobitic Crustacea Harpacticoida were highlighted: 1) the Pyrenees (Spain and France), 2) the Jura Massif (France), 3) the Alpine arc (France, Switzerland and Italy) embracing southward the River Po alluvial plain and the Slovenian External Dinarides, 4) the Central Apennines (Italy), 5) the Carpathian and Balkan mountains in Romania and at the boundary between western Bulgaria and north‐west Macedonia, 6) the Dinaric Alps (from Croatia to Albania), 7) the Sardinia Island, 8) an area in central‐northern Europe embracing Denmark, the Netherlands and Germany. The hotspots showed a clear spatial distribution in southern Europe where they were distributed predominantly south to the 45th parallel, in line to what reiteratively observed in previous studies. Many hotspots embraced more than one habitat type. The adoption of discrete groundwater habitat types as working spatial units rather than grids provided a higher resolution of where the stygobitic harpacticoid species effectively live, with the possibility of intervening more precisely to preserve them and their habitats.
... In addition to the range size, evaluation of species endemicity was used following the criteria described by Myers and De Grave (2000), because species constrained by geographical barriers are less able to cope with environmental changes than species limited by ecological requirements or physiological tolerance: ...
• Species of conservation concern are usually considered important elements in site prioritization for biodiversity conservation. To overcome the lack of information on species conservation status, multidimensional measures of species rarity can be used as proxies of species vulnerability.
• Under this assumption, a two‐step protocol for site prioritization of aquatic groundwater‐dependent ecosystems is proposed using invertebrate vulnerability estimated from species' traits. In the first step, each species occurring in the sites of interest are scored according to their vulnerability. In the second step, sites are prioritized using species' scores.
• Species vulnerability scores are based on five dimensions, for which various traits are scored: (i) geography, (ii) ecology, (iii) biology, (iv) population, and (v) evolutionary history. For each species, the scores of the various traits belonging to the same dimension are multiplied to obtain a synthetic score. These scores are then ranked into four classes and, for each dimension, each species receives a new score that reflects its rank. The sum of these scores represents the species' overall score.
• Site conservation priorities are assessed by combining species scores into three indices: Sum of Species Scores, Biodiversity Conservation Concern (which relates the sum of species scores with the local species richness) and Groundwater Biodiversity Concern (which is the average of the former two). The protocol is illustrated using case studies in Italy and it is fully implemented in the software AQUALIFE which is freely available at: http://app.aqualifeproject.eu by registered users.
• Sensitivity analyses showed that the protocol is robust against the lack of information on species biology or sampling limitations. However, trait scoring rests with the user, who must be familiar with the study group.
• This approach can be applied at any spatial scale and to different types of aquatic groundwater‐dependent ecosystems.
... Although we have used the best-studied Macaronesian marine groups, this assumption is not met for echinoderms and polychaetes, as well as for some sites (e.g., Selvagens). The method also rests on the assumption that extinction has not significantly modified the distribution pattern of each species 136 . For this analysis, we have listed all endemic species restricted to the archipelagos of Macaronesia (see Supplementary Table S7). ...
The Azores, Madeira, Selvagens, Canary Islands and Cabo Verde are commonly united under the term “Macaronesia”. This study investigates the coherency and validity of Macaronesia as a biogeographic unit using six marine groups with very different dispersal abilities: coastal fishes, echinoderms, gastropod molluscs, brachyuran decapod crustaceans, polychaete annelids, and macroalgae. We found no support for the current concept of Macaronesia as a coherent marine biogeographic unit. All marine groups studied suggest the exclusion of Cabo Verde from the remaining Macaronesian archipelagos and thus, Cabo Verde should be given the status of a biogeographic subprovince within the West African Transition province. We propose to redefine the Lusitanian biogeographical province, in which we include four ecoregions: the South European Atlantic Shelf, the Saharan Upwelling, the Azores, and a new ecoregion herein named Webbnesia, which comprises the archipelagos of Madeira, Selvagens and the Canary Islands.
... Although we have used the best-studied Macaronesian marine groups, this assumption is not met for echinoderms and polychaetes, as well as for some sites (e.g., Selvagens). The method also rests on the assumption that extinction has not significantly modified the distribution pattern of each species 136 . For this analysis, we have listed all endemic species restricted to the archipelagos of Macaronesia (see Supplementary Table S7). ...
The Azores, Madeira, Selvagens, Canary Islands and Cabo Verde are commonly united under the term "Macaronesia". This study investigates the coherency and validity of Macaronesia as a biogeographic unit using six marine groups with very different dispersal abilities: coastal fishes, echinoderms, gastropod molluscs, brachyuran decapod crustaceans, polychaete annelids, and macroalgae. We found no support for the current concept of Macaronesia as a coherent marine biogeographic unit. All marine groups studied suggest the exclusion of Cabo Verde from the remaining Macaronesian archipelagos and thus, Cabo Verde should be given the status of a biogeographic subprovince within the West African Transition province. We propose to redefine the Lusitanian biogeographical province, in which we include four ecoregions: the South European Atlantic Shelf, the Saharan Upwelling, the Azores, and a new ecoregion herein named Webbnesia, which comprises the archipelagos of Madeira, Selvagens and the Canary Islands.
... Mast & Nyffeler, 2003), including, for instance, the optimality criterion and parsimony analysis of endemism, which may be useful to disclose hierarchical relationships among areas of endemism (Fattorini, 2017). The concept of endemism itself is so controversial (Peters, 1991) that Myers & De Grave (2000) defined a complex nomenclature to distinguish among different types of endemics, but their nomenclature was inconsistently followed by later authors (see review by Fattorini, 2017). ...
Whether a species can be defined as ‘endemic’ or not, is much controversial in theoretical terms, as the concepts of ‘endemism’ and ‘area of endemism’ remain much debated across scientists. We propose that it is necessary to consider (i) an organism’s body size scale and (ii) the breadth of its distribution range if we want to define a given species as ‘endemic’ or not. So, for instance, Madagascar can be an appropriate area of endemism for animals as large and vagile as the fossa (Cryptoprocta ferox), but it is much too large for being considered an ecologically appropriate ‘area of endemism’ for small-sized frogs with limited dispersal abilities. Instead, for these small species it is ecologically more appropriate to consider given forest regions within Madagascar as ‘areas of endemism’. Therefore, we propose a five-step approach in order to define whether a given species can be considered endemic or not within a set of potential candidate species, and we offer a suite of practical examples (African squirrels, African Artiodactyla, and a family of freshwater turtles from the Americas) to elucidate the designated concept. We defined the new concept presented herein as ‘scale-dependent functional endemism’. The novel concept has the benefit of (i) including the ‘ecological characteristics’ of the target species into the concept of ‘endemism’, and (ii) being easily repeated as it is based on rather objective criteria.
... Recently, Myers and De Grave (2000) proposed a complex nomenclature to distinguish among different types of endemics, which can be summarized as follows: ...
Endemism is often misinterpreted as referring to narrow distributions (range restriction). In fact, a taxon is said to be endemic to an area if it lives there and nowhere else. The expression “endemic area” is used to identify the geographical area to which a taxon is native, whereas “area of endemism” indicates an area characterized by the overlapping distributions of two or more taxa. Among the methods used to identify areas of endemism, the optimality criterion seems to be more efficient than Parsimony Analysis of Endemism (PAE), although PAE may be useful to disclose hierarchical relationships among areas of endemism. PAE remains the best explored method and may represent a useful benchmark for testing other approaches. Recently proposed approaches, such as the analysis of nested areas of endemism, networks and neighborjoining, are promising, but need to be more widely tested. All these methods attempt to identify biogeographically homogeneous sets of areas characterized by shared species, without any attempt to evaluate their relative importance for conservation purposes. Analyses based on weighted endemism methods identify areas of endemism according to specie distributional rarity and phylogenetic position, being thus appropriate for conservation purposes. The proportion of endemic species to the total number of species living a given area is the most frequently used measure to rank areas according to their relative endemism. However, proportions obscure differences in raw numbers that can be important in conservation biology. Because the number of (endemic) species tends to increase with area, some authors proposed to model the endemics-area relationship and to consider the areas displaced above the fitting curve (i.e. those having a positive residual) as hotspots. However, the use of residuals may lead to areas being identified as hotspots for almost every size class of richness. Thus, it is important to evaluate the ability of the hotspots recovered by these procedures to really conserve total (endemic) species diversity.
Contents. – Introduction – Outline of the orders – Outline of history – Terminology and definitions. External morphology – Habitus – Size of adults – Carapace – Cephalothorax – Pleon – Telson – Integument and colour – Cephalic appendages – Thoracic appendages – Pleonal appendages. Internal morphology – Musculature – Nervous system – Sensory organs – Digestive system and digestion – Circulatory system – Respiratory system – Reproductive system – Excretory system and excretion – Endocrine organs. Reproduction and sexuality – Sexual dimorphism – Intersexuality – Sex ratio – Mating and oviposition – Fecundity – Incubation – Adjustment of reproductive parameters. Development and moulting – Marsupial development – Moulting and growth – Regeneration – Life cycle. Ecology and ethology – Habitat and distribution – Locomotion, orientation, and taxis – Migration – Social aggregation – Grooming – Food and feeding – Trophic interactions – Symbiotic associations – Parasites. Ecological and economic importance – Contribution to biodiversity – Impact on ecosystems – Importance in fisheries. Phylogeny and biogeography – Fossil record – Phylogeny – Biogeography. Systematics – Guideline on classification – Classification – Keys to the families, subfamilies, and tribes of the Lophogastrida, Stygiomysida, and Mysida. Appendix. Acknowledgements. Bibliography.
Endemic and rare species as bioindicators of habitat vulnerability were used to develop protection and management plans for biotope prioritization (mainly islands habitats, lava tubes or groundwaters). Due to their narrow distribution, the endemic species (species confined to a restricted geographic area) are more susceptible to ecological disequilibrium and habitat loss than the widespread ones. Consequently, endemics become endangered in the context of ecological disturbance caused by anthropogenic pressure, making them suitable candidates to assess environmental preservation needs. Taking into consideration that most of the stygobitic and troglobitic species are endemic and confined to specific karst areas, based on their association and frequency we propose an endemicity index (EI) adapted to the fragmented nature of the cave habitat. We used a double ranking methodology: (1) ranking the endemic species according to their frequencies in caves, and (2) ranking the caves according to their EI computed for a geographic area. Further, by mapping the caves based on their related EI, we identified the hotspots of vulnerable karst areas. The EI has been developed using as case study of 380 caves from Romania, known up to now to be inhabited by a total of 278 endemic stygobitic and troglobitic species and subspecies. In our study area, 35 out of 380 caves with endemic species, narrowly distributed to karst areas of the Carpathian massifs and Dobrogea, had a considerable high EI. The EI proves to be highly sensitive to unique taxa (endemics recorded in only one cave) and also to other endemic taxa - recorded in more than one cave. However, all the endemites are confined to a specific geographic area (in this case of study - the Carpathians and Dobrogea karst area). EI provides a reliable criterion to rank caves using the contribution of endemic species in order to assess cave and karst vulnerability and prioritize them for environment protection management.
A quantitative approach to Croizat’s panbiogeography is developed using graph theory. Croizat’s main analytical tool, the “track” (a line on a map representing the distribution of one or more taxa), is equated with the graph-theoretic concept of the minimal-spanning tree. Tracks can be represented by two different matrices that enable incongruent tracks to be detected and shared elements (biogeographic homologies) to be identified. Tracks can be orientated using both phylogenetic and biogeographic criteria. “Nodes, ” which are regions where there are large numbers of tracks, are related to the concept of the connectivity of a point. The statistical significance of track concordance can be evaluated using permutation tests of association between matrices. Previous discussions of panbiogeography have often considered panbiogeography to be a phenetic technique similar to cluster analysis using matrices of biotic similarity, or a crude precursor of vicariance biogeography. This is rejected, and the relationship between vicariance biogeography and panbiogeography is discussed. Vicariance biogeography is shown to be a clique method based on the less amenable concept of the minimal Steiner tree.
An analysis was carried out of the distributions of Hawaiian gammaridean Amphipoda of the families Aoridae and Melitidae to determine (a) whether there was a correlation between perceived dispersal potential and extent of endemicity, and (b) whether the biogeographic affinities of the two families differed. A new application of PAE is developed and applied to all families of gammaridean Amphipoda from the Indo-Pacific and Caribbean to attempt to interpret the history of space occupancy by lineages. Resulting PAE cladograms suggest a shift in the biogeographic relationships of Hawaii from the eastern Pacific and Caribbean in the past to the south west and central Pacific in modern times.
Aims to provide short working definitions of terms that come within the routine reading matter of ecologists, taxonomists, etc. Emphasis is placed on the dynamics of the biosphere - change through time. The language of taxonomy has been given thorough coverage because the subject underpins many ecological and evolutionary studies. Special attention is given to principles, processes and classifications. A wide selection of statistical terms is incorporated. After the main dictionary (c10 000 terms) there are appendices in the form of maps, diagrams, tables and lists that summarize groups of associated terms or concepts. -after Authors
Quantitative track and area cladogram methods based on Croizat’s panbiogeographic method are reviewed. A new quantitative track method based on clique and compatibility aspects of graph theory is outlined. These methods allow for statistical hypothesis testing in historical biogeography studies. A glossary is included.
Two new species of the genus Parisia Holthuis are described (P. gracilis, sp. nov., and P. unguis, sp. nov.). The relationships of these species to each other, and to the previously described species of the genus are discussed. The relationships of the species of Stygiocaris Holthuis are considered, and the occurrence of freshwater subterranean decapods in Australia is discussed in general terms.
