Do ecological communities disperse across biogeographic barriers as a unit?

Abstract

Biogeographic barriers have long been implicated as drivers of biological diversification, but how these barriers influence co-occurring taxa can vary depending on factors intrinsic to the organism and in their relationships with other species. Due to the interdependence among taxa, ecological communities present a compelling opportunity to explore how interactions among species may lead to a shared response to historical events. Here we collect single nucleotide polymorphism data from five commensal arthropods associated with the Sarracenia alata carnivorous pitcher plant, and test for codiversification across the Mississippi River, a major biogeographic barrier in the southeastern United States. Population genetic structure in three of the ecologically dependent arthropods mirrors that of the host pitcher plant, with divergence time estimates suggesting two of the species (the pitcher plant moth Exyra semicrocea and a flesh fly Sarcophaga sarraceniae) dispersed synchronously across this barrier along with the pitcher plant. Patterns in population size and genetic diversity suggest the plant and ecologically dependent arthropods dispersed from east to west across the Mississippi River. In contrast, species less dependent on the plant ecologically show discordant phylogeographic patterns. This study demonstrates that ecological relationships may be an important predictor of codiversification, and supports recent suggestions that organismal trait data should be prominently featured in comparative phylogeographic investigations.

Process‐based species delimitation leads to identification of more biologically relevant species*

“…). For the pitcher plant invertebrates from Satler and Carstens (), results corroborated previous findings in that migration models were strongly supported for both datasets. For P. viridans , the best model included secondary contact (pp = 0.944), whereas for E. semicrocea the best model included divergence with gene flow (pp = 0.798; Fig.…”

An integrated model of population genetics and community ecology

“…However, current theory either lacks an explicit population genetic foundation (Vellend, ) or considers genetic variation only of a focal taxon (Laroche et al., ). A focus on genetic diversity at the community scale offers an opportunity for ecological theory to further incorporate the potentially powerful dimension of flexible comparative phylogeographic models (Satler & Carstens, ; Xue & Hickerson, ). This should be facilitated by the increasing availability of genome‐scale phylogeographic data that allows exploration of evolutionary models of increasing complexity and explanatory power (Schraiber & Akey, ), yet such approaches have seen limited use to infer the temporal and spatial dynamics at play at the community level (but see Bunnefeld et al., ).…”

Genomic signatures of sympatric speciation with historical and contemporary gene flow in a tropical anthozoan (Hexacorallia: Actiniaria)

“…AFS calculations require fixed numbers of alleles from all populations (i.e., no missing data). Meeting this requirement would greatly decrease our data set size and probably bias our analyses, so we followed the protocol of Satler and Carstens () and Smith et al, (), requiring a locus in our AFS to be present in 75% of all individuals. To account for missing data without violating the requirements of the AFS we built our AFS as follows: (a) If a locus had fewer alleles than our threshold it was discarded, (b) if a locus had the exact number of alleles as the threshold, the minor allele frequency was recorded, and (c) if a locus exceeded the threshold, alleles were downsampled with replacement until the number of alleles met the threshold, at which point the minor allele frequency was counted.…”

“…To account for missing data without violating the requirements of the AFS we built our AFS as follows: (a) If a locus had fewer alleles than our threshold it was discarded, (b) if a locus had the exact number of alleles as the threshold, the minor allele frequency was recorded, and (c) if a locus exceeded the threshold, alleles were downsampled with replacement until the number of alleles met the threshold, at which point the minor allele frequency was counted. This approach allowed us to maximize the number of SNPs used to build the AFS, but also has the potential to lead to monomorphic alleles based on the downsampling procedure (see Satler & Carstens, ). Thus, we repeated the AFS building procedure 10 times, allowing us to account for variation in the downsampling process during model selection, but also allowing us to calculate confidence intervals on our parameter estimates (Satler & Carstens, ; Smith et al, ).…”

“…This approach allowed us to maximize the number of SNPs used to build the AFS, but also has the potential to lead to monomorphic alleles based on the downsampling procedure (see Satler & Carstens, ). Thus, we repeated the AFS building procedure 10 times, allowing us to account for variation in the downsampling process during model selection, but also allowing us to calculate confidence intervals on our parameter estimates (Satler & Carstens, ; Smith et al, ).…”