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Metapopulation Genetics and the Evolution of Dispersal
Abstract
A Markovian extinction model that takes into account age structure of local populations allows consideration of the effects of demography and successional dynamics on the evolution of migration. Analytical expressions for the evolutionarily stable (ES) rates of dispersal are given for cases in which newly recolonized sites attain carrying capacity within a single season. Using a low-fecundity numerical model, we find that an increase of the level of site saturation increases the dispersal rate. Ecological successions and unequal local extinction rates between newly colonized sites and established populations strongly affect the ES dispersal rate. The frequency of genetic modifiers that enhance the rate of dispersal evolves negative correlations with deme age, with high-migration genotypes predominant among colonizers while progressively declining in frequency as a deme ages. This suggests that between-deme selection (colonization) favors migrants while within-deme selection favors low dispersers, which allows the coexistence of types with different dispersal rates. Because of the interaction between the two levels of selection, the relation between the ES dispersal rate and the deme maximal lifetime is nonmonotone. We suggest that life-history traits other than dispersal might also experience antagonistic selective forces at the between- and within-deme levels.
... Many species have adapted different dispersal probabilities, distances or habitat selection in nature, suggesting that this trait commonly evolves under varying landscape contexts [49][50][51][52][53]. Understanding the evolution of dispersal requires a view that extends beyond the typical limits of the local population and embraces a multi-patch perspective that includes the availability of high-fitness habitats external to the population and considers the costs accrued during transit to these habitats [17,56,57]. Dispersal evolution can thus be intricately tied to changes in habitat quality across landscapes and the ability to move across unsuitable habitats [50,[56][57][58]. ...
... Many species have adapted different dispersal probabilities, distances or habitat selection in nature, suggesting that this trait commonly evolves under varying landscape contexts [49][50][51][52][53]. Understanding the evolution of dispersal requires a view that extends beyond the typical limits of the local population and embraces a multi-patch perspective that includes the availability of high-fitness habitats external to the population and considers the costs accrued during transit to these habitats [17,56,57]. Dispersal evolution can thus be intricately tied to changes in habitat quality across landscapes and the ability to move across unsuitable habitats [50,[56][57][58]. As a result, dispersal can be considered a metapopulation adaptation that responds to selection at landscape scales. ...
... These models find that dispersal probability often evolves to higher levels to take advantage of open, competition-free patches [37,60]. Other models that evaluate the impact of patch extinctions on dispersal evolution also find that the availability of open, competition-free patches selects for the evolution of higher dispersal [50,[56][57][58]. In general, we can expect that lower competition in both single-species metapopulations and multi-species metacommunities can select for the evolution of higher dispersal. ...
Biologists have long sought to predict the distribution of species across landscapes to understand biodiversity patterns and dynamics. These efforts usually integrate ecological niche and dispersal dynamics, but evolution can also mediate these ecological dynamics. Species that disperse well and arrive early might adapt to local conditions, which creates an evolution-mediated priority effect that alters biodiversity patterns. Yet, dispersal is also a trait that can evolve and affect evolution-mediated priority effects. We developed an individual-based model where populations of competing species can adapt not only to local environments but also to different dispersal probabilities. We found that lower regional species diversity selects for populations with higher dispersal probabilities and stronger evolution-mediated priority effects. When all species evolved dispersal, they monopolized fewer patches and did so at the same rates. When only one of the species evolved dispersal, it evolved lower dispersal than highly dispersive species and monopolized habitats once freed from maladaptive gene flow. Overall, we demonstrate that dispersal evolution can shape evolution-mediated priority effects when provided with a greater ecological opportunity in species-poor communities. Dispersal- and evolution-mediated priority effects probably play greater roles in species-poor regions like the upper latitudes, isolated islands and in changing environments.
This article is part of the theme issue 'Diversity-dependence of dispersal: interspecific interactions determine spatial dynamics'.
... As a consequence, the optimal dispersal distance must be large enough to override the degree of habitat aggregation (Hamilton and May, 1977;Levin et al., 1984). Olivieri et al. (1995) pointed out, however, that a predictably perennial habitat with a very low frequency of occurrence may rapidly favor the coexistence of highly dispersive and nondispersive stages. Indeed, dispersing individuals carrying "highmigration genotypes" will leave local populations and such genotypes will thus be rapidly lost in the local populations while they will be overrepresented in newly colonized sites (Olivieri et al., 1995). ...
... Olivieri et al. (1995) pointed out, however, that a predictably perennial habitat with a very low frequency of occurrence may rapidly favor the coexistence of highly dispersive and nondispersive stages. Indeed, dispersing individuals carrying "highmigration genotypes" will leave local populations and such genotypes will thus be rapidly lost in the local populations while they will be overrepresented in newly colonized sites (Olivieri et al., 1995). The two dispersal strategies may thus co-exist in a metapopulation as a result of opposite selective processes within and between populations. ...
In highly fragmented and relatively stable cold-seep ecosystems, species are expected to exhibit high migration rates and long-distance dispersal of long-lived pelagic larvae to maintain genetic integrity over their range. Accordingly, several species inhabiting cold seeps are widely distributed across the whole Atlantic Ocean, with low genetic divergence between metapopulations on both sides of the Atlantic Equatorial Belt (AEB, i.e. Barbados and African/European margins). Two hypotheses may explain such patterns: (i) the occurrence of present-day gene flow or (ii) incomplete lineage sorting due to large population sizes and low mutation rates. Here, we evaluated the first hypothesis using the cold seep mussels Gigantidas childressi, G. mauritanicus, Bathymodiolus heckerae and B. boomerang. We combined COI barcoding of 763 individuals with VIKING20X larval dispersal modelling at a large spatial scale not previously investigated. Population genetics supported the parallel evolution of Gigantidas and Bathymodiolus genera in the Atlantic Ocean and the occurrence of a 1-3 Million-year-old vicariance effect that isolated populations across the Caribbean Sea. Both population genetics and larval dispersal modelling suggested that contemporary gene flow and larval exchanges are possible across the AEB and the Caribbean Sea, although probably rare. When occurring, larval flow was eastward (AEB - only for B. boomerang) or northward (Caribbean Sea - only for G. mauritanicus). Caution is nevertheless required since we focused on only one mitochondrial gene, which may underestimate gene flow if a genetic barrier exists. Non-negligible genetic differentiation occurred between Barbados and African populations, so we could not discount the incomplete lineage sorting hypothesis. Larval dispersal modelling simulations supported the genetic findings along the American coast with high amounts of larval flow between the Gulf of Mexico (GoM) and the US Atlantic Margin, although the Blake Ridge population of B. heckerae appeared genetically differentiated. Overall, our results suggest that additional studies using nuclear genetic markers and population genomics approaches are needed to clarify the evolutionary history of the Atlantic bathymodioline mussels and to distinguish between ongoing and past processes.
... Spatial selection is interesting as it can lead to accelerating range expansions which may explain the rapid recolonization of trees in temperate latitudes since the last glacial period (Reid's paradox; see [60]). The evolution of higher dispersal rates at the invasion front is also reminiscent of the evolution of lower dispersal in ageing demes [61] -in both cases, newly colonised patches harbour individuals with higher dispersal rates than older ones. ...
Dispersal is a well-recognized driver of ecological and evolutionary dynamics, and simultaneously an evolving trait. Dispersal evolution has traditionally been studied in single-species metapopulations so that it remains unclear how dispersal evolves in metacommunities and metafoodwebs, which are characterized by a multitude of species interactions. Since most natural systems are both species-rich and spatially structured, this knowledge gap should be bridged. Here, we discuss whether knowledge from dispersal evolutionary ecology established in single-species systems holds in metacommunities and metafoodwebs and we highlight generally valid and fundamental principles. Most biotic interactions form the backdrop to the ecological theatre for the evolutionary dispersal play because interactions mediate patterns of fitness expectations across space and time. While this allows for a simple transposition of certain known principles to a multispecies context, other drivers may require more complex transpositions, or might not be transferred. We discuss an important quantitative modulator of dispersal evolution—increased trait dimensionality of biodiverse meta-systems—and an additional driver: co-dispersal. We speculate that scale and selection pressure mismatches owing to co-dispersal, together with increased trait dimensionality, may lead to a slower and more ‘diffuse’ evolution in biodiverse meta-systems. Open questions and potential consequences in both ecological and evolutionary terms call for more investigation.
This article is part of the theme issue 'Diversity-dependence of dispersal: interspecific interactions determine spatial dynamics'.
... There is a large body of the literature on the evolution and ecology of migration and dispersal [45][46][47][48][49], especially for population structures formed by islands (also called patches, demes or metapopulations) [50][51][52][53]. The present framework provides a formal way to approach the motility potential as a genotypic quality. ...
Natural selection is usually studied between mutants that differ in reproductive rate, but are subject to the same population structure. Here we explore how natural selection acts on mutants that have the same reproductive rate, but different population structures. In our framework, population structure is given by a graph that specifies where offspring can disperse. The invading mutant disperses offspring on a different graph than the resident wild-type. We find that more densely connected dispersal graphs tend to increase the invader’s fixation probability, but the exact relationship between structure and fixation probability is subtle. We present three main results. First, we prove that if both invader and resident are on complete dispersal graphs, then removing a single edge in the invader’s dispersal graph reduces its fixation probability. Second, we show that for certain island models higher invader’s connectivity increases its fixation probability, but the magnitude of the effect depends on the exact layout of the connections. Third, we show that for lattices the effect of different connectivity is comparable to that of different fitness: for large population size, the invader’s fixation probability is either constant or exponentially small, depending on whether it is more or less connected than the resident.
... So far no invasion criterion could be established rigorously for models of hydrodynamics limits or moments. Invasion fitness in metapopulations has been worked out by Olivieri et al. (1995) and in greater generality by Metz and Gyllenberg (2000). However, as we already pointed out, such models do not account for limited dispersal and therefore address spatial processes in a rather special way. ...
Habitat fragmentation and global climate change are the two major environmental threats to the persistence of species and ecosystems. The probability of a species surviving such changes is strongly dependent on its ability to track shifts in the environmental, either by moving between patches of habitat or by rapidly adapting to local condition. These 'solutions' to problems posed by environmental change depend on dispersal propensity, motivating our desire to better understand this important behavior. This book is a comprehensive overview of the new developments in the study of dispersal and the state-of-the-art research on the evolution of this trait. The causes, mechanisms, and consequences of dispersal at the individual , population, and species levels are considered. The promise of new techniques and models for studying dispersal, drawn from molecular biology and demography is explored. Perspectives on the study of dispersal are offered from evolution, conservation biology, and genetics. Throughout the book, theoretical approaches are combined with empirical data, and examples are included from as wide a range of species as possible.
... These models partition environments into discrete, interconnected sites while modeling the internal dynamics of each site as "well-mixed." Metapopulation models were able to incorporate feedbacks between migration rates and the distributions of genes that determine those migration rates (Asmussen, 1983;Balkau & Feldman, 1973;Ludwig & Levin, 1991;Moody, 1981;Nagylaki & Moody, 1980;Olivieri et al., 1995). In models where environmental characteristics were allowed to vary from site to site (Cohen & Levin, 1991;Hastings, 1983;Holt, 1985;Levin et al., 1984;McPeek & Holt, 1992), heterogeneity was repeatedly shown to reduce dispersal abilities (Kirkland et al., 2006;Murrell et al., 2002;Papaïx et al., 2013). ...
We consider the spatial propagation and genetic evolution of model populations comprising multiple subpopulations, each distinguished by its own characteristic dispersal rate. Mate finding is modeled in accord with the assumption that reproduction is based on random encounters between pairs of individuals, so that the frequency of interbreeding between two subpopulations is proportional to the product of local population densities of each. The resulting nonlinear growth term produces an Allee effect, whereby reproduction rates are lower in sparsely populated areas; the distribution of dispersal rates that evolves is then highly dependent upon the population's initial spatial distribution. In a series of numerical test cases, we consider how these dynamics affect lattice-like arrangements of population fragments, and investigate how a population's initial fragmentation determines the dispersal rates that evolve as a habitat is colonized. First, we consider a case where initial population fragments coincide with habitat islands, within which death rates differ from those that apply outside; the presence of inhospitable exterior regions exaggerates Allee effect-driven reductions in dispersal ability. We then examine how greater distances separating adjacent population fragments lead to more severe reductions in dispersal ability. For populations of a fixed initial magnitude, fragmentation into smaller, denser patches leads not only to greater losses of dispersal ability, but also helps ensure the population's long-term persistence, emphasizing the trade-offs between the benefits and risks of rapid dispersal under Allee effects. Next, simulations of well-established populations disrupted by localized depopulation events illustrate how mate-finding Allee effects and spatial heterogeneity can drive a population's dispersal ability to evolve either downward or upward depending on conditions, highlighting a qualitative distinction between population fragmentation and habitat heterogeneity. A final test case compares populations that are fragmented across multiple scales, demonstrating how differences in the relative scales of micro- and macro-level fragmentation can lead to qualitatively different evolutionary outcomes.
... A hostile landscape matrix increases dispersal risks and may result in selection pressures that prioritize reproduction within habitat fragments while decreasing seed dispersal investment (Bonte et al., 2012). On the one hand, limitation of the seed dispersal potential can lead to selection pressures which improve dispersal mechanisms in order to avoid inbreeding depression (Cote et al., 2017;Olivieri et al., 1995). Smaller plant population sizes, lower flower densities and increased spatial isolation disrupt plant-pollinator mutualisms in fragmented habitats (Aguilar et al., 2006;Eriksson & Ehrlen, 2001;Gómez-Martínez et al., 2020;Kwak et al., 1998). ...
Climate change and the resulting increased drought frequencies pose considerable threats to forest herb populations, particularly where additional environmental challenges jeopardize responses to selection. Specifically, habitat fragmentation may impede climate adaptation through its impact on the distribution of adaptive genetic variation, and cause evolutionary shifts in mating systems. To assess how habitat fragmentation disrupts climate adaptation, we conducted a common garden experiment with Primula elatior offspring originating from 24 populations sampled along a latitudinal gradient with varying climate and landscape characteristics. We then quantified a range of vegetative, regulatory, and reproductive traits under distinct soil moisture regimes to evaluate imprints of local adaptation and phenotypic plasticity. Additionally, we conducted a more extensive field campaign in 60 populations along the same latitudinal gradient to evaluate the potential evolutionary breakdown of reciprocal herkogamy. For large, connected populations, our results demonstrated an evolutionary shift from a drought avoidance strategy in southern populations to a drought tolerance strategy in northern populations. However, habitat fragmentation disrupted climate clines and the adaptive responses to drought stress in key traits related to growth, biomass allocation and water regulation. Additionally, our findings indicate the onset of evolutionary breakdown in reciprocal herkogamy and divergence in other key flower traits. The disruption of climate clines, drought responses, and adaptations in mating systems contributed to a substantially diminished flowering investment across the distribution range, with the most pronounced effects observed in southern fragmented populations. We present novel empirical evidence of how habitat fragmentation disrupts climate adaptation and drought tolerance in a wide range of traits along the range of the forest herb Primula elatior. These findings emphasize the need to account for habitat fragmentation while designing effective conservation strategies in order to preserve and restore resilient meta-populations of forest herbs amidst ongoing global changes.
Climate change and the resulting increased drought frequencies pose considerable threats to forest herb populations, particularly where additional environmental challenges jeopardize responses to selection. Specifically, habitat fragmentation may hamper climate adaptation by altering the distribution of adaptive genetic variation and may also induce evolutionary changes in mating systems.
To assess how habitat fragmentation disrupts climate adaptation, we conducted a common garden experiment with Primula elatior offspring originating from 24 populations sampled along a latitudinal gradient with varying climate and landscape characteristics. We then quantified a range of vegetative, regulatory and reproductive traits under distinct soil moisture regimes to evaluate imprints of local adaptation and phenotypic plasticity. Additionally, we conducted a more extensive field campaign in 60 populations along the same latitudinal gradient to evaluate the potential evolutionary breakdown of reciprocal herkogamy.
For large, connected populations, our results demonstrated an evolutionary shift from a strategy in southern populations that seems aligned with drought avoidance—where plants minimize their exposure to dry conditions and optimize photosynthesis—to a drought tolerance strategy in northern populations, where plants are adapted to function despite water scarcity. However, habitat fragmentation disrupted climate clines and the adaptive responses to drought stress in key traits related to growth, biomass allocation and water regulation. Additionally, our findings indicate the onset of evolutionary breakdown in reciprocal herkogamy and divergence in other key flower traits. The disruption of climate clines, drought responses and adaptations in mating systems contributed to a substantially diminished flowering investment across the distribution range, with the most pronounced effects observed in southern fragmented populations.
Synthesis. We present novel empirical evidence of how habitat fragmentation disrupts climate adaptation and drought tolerance in a wide range of traits along the range of the forest herb Primula elatior. These findings emphasize the need to account for habitat fragmentation while designing effective conservation strategies in order to preserve and restore resilient meta‐populations of forest herbs amidst ongoing global changes.
The metapopulation perspective is an important conceptual framework in ecology, biogeography, and evolutionary ecology. Metapopulations are spatially distributed populations linked by dispersal. Both metapopulation models and their community and ecosystem level analogues, metacommunity and meta-ecosystem models, tend to be more stable regionally than locally and display an enhancement in abundance because of the interplay of spatio-temporal heterogeneity and dispersal (an effect that has been called the "inflationary effect"). We highlight the essential role of spatio-temporal heterogeneity in metapopulation biology, sketch empirical demonstrations of the inflationary effect, and provide a mechanistic interpretation of how the inflationary effect arises and impacts population growth and abundance. The spread of infectious disease is used to illustrate how this effect, emerging from the interplay of spatiotemporal variability and dispersal, can have serious real-world consequences. Namely, failure to recognize the full possible effects of spatio-temporal heterogeneity likely enhanced the spread of COVID-19, and a comparable lack of understanding of emergent population processes at large scales may hamper the control and eradication of other infectious diseases. We finish by noting how the effects of spatio-temporal heterogeneity, including the inflationary effect, have implicitly played roles in many traditional themes in the history of ecology. The inflationary effect is implicit in processes explored in subdisciplines as far ranging as natural enemy-victim dynamics, species coexistence, and conservation biology. Seriously confronting the complexity of spatiotemporal heterogeneity has the potential to push many of these subdisciplines forward.
Both within and among species of milkweed bugs, Oncopeltus (subgenus Erythrischius), tropical forms are smaller than temperate and island are smaller then mainland. These differences were determined from measurements on field collected and laboratory reared bugs and from museum specimens. Laboratory rearing in constant environments indicated that the differences observed among populations and species are heritable and presumably adaptive. Variation in size between island and among continental populations of O. fasciatus were not always in predicted directions and are presumably influenced by local conditions, especially environmental heterogeneity (temporal and spatial variability). Tests for flight potential using tethered insects also indicated significant differences among species and populations. Tropical species and tropical populations of O. fasciatus flew less than temperate populations of O. fasciatus. These generally low flight performances of the tropical bugs presumably reflect adaptation to relatively equable and predictable habitats with little selection for long-distance migration. In contrast, migration is a necessity for temperate zone bugs since they cannot survive the winter Intermediate levels of flight were observed in bugs of Florida origin and, along with a variable diapause (Dingle et al., 1980), is probably a reflection of unpredictability in Florida climate and habitats. The least flight was recorded in bugs from the islands of Puerto Rico and Guadeloupe, consistent with many observations of flightlessness in island insects. In general there was an association between larger size and longer flight. Of the tropical species, the largest is O. sandarachatus which also displays the longest flights. Since this species cannot survive on Barbados because of the destruction of its host plants (Blakley and Dingle, 1978), bugs captured there were probably migrants, accounting for their large size relative to a Trinidad sample. Northern and migrant O. fasciatus are also generally larger, but large Florida and on the average small, but highly variable, Maryland bugs are evidently strongly influenced by local conditions which confound general trends. A number of competition, convergence, or clinal models fail to explain size differences in Oncopeltus. Larger bugs survive starvation longer (Blakley, 1977) suggesting that large size may be an advantage during food deprivation and other stresses arising during migration or diapause. A direct association between size and flight with populations of the same geographic origin remains to be tested.
Simple mathematical models show that adaptations for achieving dispersal
retain great importance even in uniform and predictable environments. A
parent organism is expected to try to enter a high fraction of its
propagules into competition for sites away from its own immediate
locality even when mortality to such dispersing propagules is extremely
high. The models incidentally provide a case where the evolutionarily
stable dispersal strategy for individuals is suboptimal for the
population as a whole.
Danthonia spicata produces both chasmogamous and cleistogamous flowers. Seeds from both types of flowers were collected by family from a natural population. The seeds were germinated and the resulting plants divided into ramets that were raised both in the greenhouse and in the field. The proportion of cleistogamous flowers produced by each plant was determined the following spring when the plants flowered. All plants produced both types of flowers. The percentage of cleistogamous flowers ranged from 12-65%. Plants in the greenhouse produce, on average, 12% more cleistogamous flowers than field plants. The variation in the percent cleistogamous flowers had a large genetic component; the broad sense heritability was 52.6% in the field and 71.6% in the greenhouse. Absolute numbers of cleistogamous and chasmogamous flowers had lower heritabilities. -from Author
In order to determine if red maple dispersal potential or seed size change during secondary succession, samaras were collected from five populations located in early successional environments and five populations located in late successional environments. Wing loading ratios (samara mass-mg/samara area-cm(2)), which are inversely proportional to dispersal ability, were computed for all samaras, and seeds were excised from each samara and weighed. Samaras from the early successional red maples showed slightly but significantly lower wing loading ratios than those from the late successional environments. This result corresponds with the conclusions reached by several theoretical investigations of seed dispersal evolution that predict that recently founded populations will show greater dispersal abilities than more established populations. The earlier successional populations had slightly heavier seeds than the later successional populations, which suggests that the changes in community composition and dynamics that occur during this successional sequence do not select for heavier seeds in older red maple populations. Coefficients of variation for wing loading and seed size showed no consistent trends with successional stage, which indicates that variation in these characters does not decrease as succession proceeds.
Coexistence mechanisms of two co-occurring species of Proteaceae, Protea lepidocarpodendron and Leucospermum conocarpodendron, were studied. Both are tall, arborescent shrubs forming the overstory of the fynbos communities in which they occur. Seeds of L. conocarpodendron are dispersed by ants while those of P. lepidocarpodendron are dispersed by wind. The seedlings compete for space made available after periodic fires. Seedlings of the ant-dispersed species are scarce under the skeletons of the wind-dispersed species after a fire but relatively common in open sites. In contrast, seedlings of the wind-dispersed species are densest under their own skeletons and rare in open sites. Seedlings of the ant-dispersed species are outgrown by their wind-dispersed competitors and suffer reduced fecundity and increased mortality when they co-occur. The adult survival of the ant-dispersed species in light fires is also reduced when it establishes under or next to the wind-dispersed species. A Markovian model of the system suggests that ant dispersal of Leucospermum seed reduces the rate of competitive exclusion by Protea but is not sufficient to explain the persistence of the former in this system. To persist, Leucospermum requires open space, which is made available either by adult survival in light fires which set back its Protea competitor or by survival as seed banks through burns that destroy the seed banks of Protea.
Seed size, dormancy, and dispersal share 3 population-dynamic functions in temporally and spatially varying environments: risk reduction of bet hedging, escape from crowding, and escape from sib competition. A model was developed to explore ways they may interact to reduce risk. The risk-reducing properties of these seed traits evolve only in response to global temporal variance. Thus, to understand how selection impinges on the seed traits, creating fitness interactions, one must understand the factors contributing to global temporal variance and how they are mitigated by the various seed traits. Since the traits interact to reduce variance, arbitarily fixing any 1 trait at different values alters the fitness-maximizing values of the others, resulting in trade-offs among traits. The authors explore how changes in the number of independent environmental patches, probability of favorable conditions, radius of dispersal, and spatial and temporal autocorrelation of environmental conditions alter selection on the interacting syndrome of seed traits. -from Authors
Extinction rates and the composition of colonizing groups were investigated for Tetraopes tetraophthalmus (Coleoptera: Cerambycidae). Four of 33 natural populations became extinct over 6 yr of observation, yielding an extinction probability of c2% per generation, sufficient to influence population structure. Study of migration into 8 experimental patches of milkweed showed that an average of 3 beetles invade an unoccupied site each year, ie significant genetic drift could be associated with the founding of populations. Variation about this average was significant from site to site and from year to year, tending to reduce the average effective number of colonists. Although the sex ratio of colonists, pooled across sites and years, was close to 50:50, significant but opposite deviations from this ratio were observed in 2 of 3 yr. Individuals migrating into patches persisted for 6 days, on average. The relative isolation of some of the experimental patches from potential sources of the migrants demonstrated that at least occasional dispersal events on the order of several kilometers occur in this species, raising the possibility that considerable gene flow could also be associated with the founding events. -from Author