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opennotspecifiedJul 2020View details →

FIGURE 1 in New troglobitic and troglophilic syntopic species of Endecous (Orthoptera, Grylloidea, Phalangopsidae) from a Brazilian cave: a case of sympatric speciation?

FIGURE 1 (A and B). (A) Type locality of Endecous species from South America (excepting Minas Gerais State); (B) Type locality of Endecous species from Minas Gerais State. (*) Uncertain locality, possibly between the border between the States of Minas Gerais and Bahia, described for the first time as "Sierra Geral".

opennotspecifiedJul 2020View details →

FIGURES 20–25 in New troglobitic and troglophilic syntopic species of Endecous (Orthoptera, Grylloidea, Phalangopsidae) from a Brazilian cave: a case of sympatric speciation?

FIGURES 20–25. Right tegmen of Endecous (Pedroecous) didymus n. sp. in dorsal and lateral view. 20–holotype (ISLA 43330); 21–paratype (ISLA 15696); 22–paratype (ISLA 15697); 23–paratype (ISLA 43329); 24–paratype (ISLA 43336) and 25–paratype (ISLA 43338).

opencc-zeroJul 2020View details →

Data from: Ecological speciation in sympatric palms: 3. genetic map reveals genomic islands underlying species divergence in Howea

Although it is now widely accepted that speciation can occur in the face of continuous gene flow, with little or no spatial separation, the mechanisms and genomic architectures that permit such divergence are still debated. Here, we examined speciation in the face of gene flow in the Howea palms of Lord Howe Island, Australia. We built a genetic map using a novel method applicable to long-lived tree species, combining it with double digest restriction-site associated DNA sequencing of multiple individuals. Based upon various metrics, we detected 46 highly differentiated regions throughout the genome, some of which contained genes with functions that are particularly relevant to the speciation scenario for Howea, specifically salt and drought tolerance.

opencc-zeroDec 2015View details →

Data from: Are sympatrically speciating Midas cichlid fish special? Patterns of morphological and genetic variation in the closely related species Archocentrus centrarchus

Established empirical cases of sympatric speciation are scarce, although there is an increasing consensus that sympatric speciation might be more common than previously thought. Midas cichlid fish are one of the few substantiated cases of sympatric speciation, and they formed repeated radiations in crater lakes. In contrast, in the same environment, such radiation patterns have not been observed in other species of cichlids and other families of fish. We analyze morphological and genetic variation in a cichlid species (Archocentrus centrarchus) that co-inhabits several crater lakes with the Midas species complex. In particular, we analyze variation in body and pharyngeal jaw shape (two ecologically important traits in sympatrically divergent Midas cichlids) and relate that to genetic variation in mitochondrial control region and microsatellites. Using these four datasets, we analyze variation between and within two Nicaraguan lakes: a crater lake where multiple Midas cichlids have been described and a lake where the source population lives. We do not observe any within-lake clustering consistent across morphological traits and genetic markers, suggesting the absence of sympatric divergence in A. centrarchus. Genetic differentiation between lakes was low and morphological divergence absent. Such morphological similarity between lakes is found not only in average morphology, but also when analyzing covariation between traits and degree of morphospace occupation. A combined analysis of the mitochondrial control region in A. centrarchus and Midas cichlids suggests that a difference between lineages in the timing of crater lake colonization cannot be invoked as an explanation for the difference in their levels of diversification. In light of our results, A. centrarchus represents the ideal candidate to study the genomic differences between these two lineages that might explain why some lineages are more likely to speciate and diverge in sympatry than others.

opencc-zeroDec 2009View details →

Data from: Parallel polyploid speciation: distinct sympatric gene-pools of recurrently derived allo-octoploid Asplenium ferns

Although polyploidy is widespread, its significance to the generation of biodiversity remains unclear. Many polyploids have been derived recurrently. For a particular polyploid, gene-flow between the products of independent origin is typical where they come into contact. Here, we use AFLP DNA-fingerprinting and chloroplast DNA sequences to demonstrate parallel polyploid speciation within both of the ferns Asplenium cimmeriorum and A. gracillimum. Both of these taxa comprise at least two allopolyploids, recurrently derived from the same progenitor pair. Each of these allopolyploids remain genetically distinguishable even with extensive sympatry, and could therefore be considered distinct species. To our knowledge, parallel speciation on this scale amongst recurrent polyploids has not been previously reported. With their parallel origins, these 'evolutionary replicates' provide an unrivalled opportunity to investigate how the reproductive barriers and ecological differentiation necessary for speciation arise following polyploidy.

opencc-zeroDec 2011View details →

Data from: On the scent of standing variation for speciation: behavioral evidence for native sympatric host races of Rhagoletic pomonella (Diptera: Tephritidae) in the southern United States

Standing variation can be critical for speciation. Here, we investigate the origins of fruit odor discrimination for Rhagoletis pomonella underlying the fly's sympatric shift in the northeastern U.S. from downy hawthorn (Crataegus mollis) to apple (Malus domestica). Because R. pomonella mate on host fruit, preferences for natal fruit volatiles generate prezygotic isolation. Apples emit volatiles that appear to be missing from gas chromatography/electroantennographic detection profiles for flies infesting downy hawthorns, raising the question of how R. pomonella evolved a preference for apple. In the southern U.S., R. pomonella attacks several native hawthorns. Behaviorally active volatile blends for R. pomonella infesting southern hawthorns contain the missing apple volatiles, potentially explaining why downy hawthorn flies could have evolved to be sensitive to a blend of apple volatiles. Flight tunnel assays imply that southern hawthorn populations were not the antecedent of a preassembled apple race, as southern flies were not attracted to the apple volatile blend. Instead, behavioral evidence was found for southern host races on native hawthorns, complementing the story of the historical sympatric shift to introduced apple in the North and illustrating how R. pomonella may evolve novel combinations of agonist and antagonist responses to volatiles to utilize new fruit resources.

opencc-zeroDec 2011View details →

Data from: Weak disruptive selection and incomplete phenotypic divergence in two classic examples of sympatric speciation: Cameroon crater lake cichlids

Recent documentation of a few compelling examples of sympatric speciation led to a proliferation of theoretical models. Unfortunately, plausible examples from nature have rarely been used to test model predictions, such as the initial presence of strong disruptive selection. Here I estimated the form and strength of selection in two classic examples of sympatric speciation: radiations of Cameroon cichlids restricted to lakes Barombi Mbo and Ejagham. I measured five functional traits and relative growth rates in over 500 individuals within incipient species complexes from each lake. Disruptive selection was prevalent in both groups on single and multivariate trait axes, but weak relative to stabilizing selection on other traits and most published estimates of disruptive selection. Furthermore, despite genetic structure, assortative mating, and bimodal species-diagnostic coloration, trait distributions were unimodal in both species complexes, indicating the earliest stages of speciation. Long waiting times or incomplete sympatric speciation may result when disruptive selection is initially weak. Alternatively, I present evidence of additional constraints in both species complexes, including weak linkage between coloration and morphology, reduced morphological variance aligned with nonlinear selection surfaces, and minimal ecological divergence. While other species within these radiations show complete phenotypic separation, morphological and ecological divergence in these species complexes may be slow or incomplete outside optimal parameter ranges, in contrast to rapid divergence of their sexual coloration.

opencc-zeroDec 2017View details →

Data from: Flickers of speciation? Sympatric color morphs of the arc-eye hawkfish, Paracirrhites arcatus, reveal key elements of divergence-with-gene-flow

One of the primary challenges of evolutionary research is to identify ecological factors that favor reproductive isolation. Therefore, studying partially isolated taxa has the potential to provide novel insight into the mechanisms of evolutionary divergence. Our study utilizes an adaptive color polymorphism in the arc-eye hawkfish (Paracirrhites arcatus) to explore the evolution of reproductive barriers in the absence of geographic isolation. Dark and light morphs are ecologically partitioned into basaltic and coral microhabitats a few meters apart. To test whether ecological barriers have reduced gene flow among dark and light phenotypes, we evaluated genetic variation at 30 microsatellite loci and a nuclear exon (Mc1r) associated with melanistic coloration. We report low, but significant microsatellite differentiation among color morphs and stronger divergence in the coding region of Mc1r indicating signatures of selection. Critically, we observed greater genetic divergence between color morphs on the same reefs than between the same morphs in different geographic locations. We hypothesize that adaptation to the contrasting microhabitats is overriding gene flow and is responsible for the partial reproductive isolation observed between sympatric color morphs. Combined with complementary studies of hawkfish ecology and behavior, these genetic results indicate an ecological barrier to gene flow initiated by habitat selection and enhanced by assortative mating. Hence the arc-eye hawkfish fulfill theoretical expectations for the earliest phase of speciation-with-gene-flow.

Fig. 8 Fitness landscape for models 7 and 8 in Modelling sympatric speciation by means of biologically plausible mechanistic processes as exemplified by threespine stickleback species pairs

Fig. 8 Fitness landscape for models 7 and 8. Relative fitness is a function of trait T1 and trait T2. Epistasis is modelled as follows:

Fig. 5 The probability that a female accepts a in Modelling sympatric speciation by means of biologically plausible mechanistic processes as exemplified by threespine stickleback species pairs

Fig. 5 The probability that a female accepts a male as a mate is a function of the morphological difference between them, and her stringency of choosiness S (here T ¼ S þ 0: 25), as in model 4 (variants applied in models 6 and 8). In the figure, 3 values of S are shown; S can have all values that are averages of two allelic values (from 64 or 256 equidistant values from 0 to 1)

Fig. 3 Model 1. a in Modelling sympatric speciation by means of biologically plausible mechanistic processes as exemplified by threespine stickleback species pairs

Fig. 3 Model 1. a Typical initial distribution of the allelic values at generation 0. b Typical distribution of the allelic values at generation 100. c Typical distribution of T, the phenotypic values, at generation 100. Nm = Nf =100; σ =0.25; μ = 1%; n = 256 alleles. Similar results were obtained in 20 out of 20 replicate simulations with σ =0.25, in 13 out of 20 replicate simulations with σ =0.5, and in 0 out of 10 replicate simulations with σ =1

Fig. 6 Model 4 in Modelling sympatric speciation by means of biologically plausible mechanistic processes as exemplified by threespine stickleback species pairs

Fig. 6 Model 4: Reinforcement of stringency of assortative mating. Columns: 1 Typical distribution of morphology alleles; 2 typical distribution of morphology phenotypes T; 3 typical distribution of stringency of choosiness alleles. Rows: 1 Generation 0, 2 generation

opencc-zeroDec 2014View details →

Data from: Complex histories of repeated gene flow in Cameroon crater lake cichlids cast doubt on one of the clearest examples of sympatric speciation

One of the most celebrated examples of sympatric speciation in nature are monophyletic radiations of cichlid fishes endemic to Cameroon crater lakes. However, phylogenetic inference of monophyly may not detect complex colonization histories involving some allopatric isolation, such as double invasions obscured by genome-wide gene flow. Population genomic approaches are better suited to test hypotheses of sympatric speciation in these cases. Here we use comprehensive sampling from all four sympatric crater lake cichlid radiations in Cameroon and outgroups across Africa combined with next-generation sequencing to genotype tens of thousands of SNPs. We find considerable evidence of gene flow between all four radiations and neighboring riverine populations after initial colonization. In a few cases, some sympatric species are more closely related to outgroups than others, consistent with secondary gene flow facilitating their speciation. Our results do not rule out sympatric speciation in Cameroon cichlids, but rather reveal a complex history of speciation with gene flow, including allopatric and sympatric phases, resulting in both reproductively isolated species and incipient species complexes. The best remaining non-cichlid examples of sympatric speciation all involve assortative mating within microhabitats. We speculate that this feature may be necessary to complete the process of sympatric speciation in nature.

opencc-zeroDec 2011View details →

Data from: Recent speciation between sympatric Tanganyikan cichlid color morphs

Lake Tanganyika, Africa's oldest lake, harbors an impressive diversity of cichlid fishes. Although diversification in its radiating groups is thought to have been initially rapid, cichlids from Lake Tanganyika show little evidence for ongoing speciation. In contrast, examples of recent divergence among sympatric color morphs are well known in haplochromine cichlids from Lakes Malawi and Victoria. Here we report genetic evidence for recent divergence between two sympatric Tanganyikan cichlid color morphs. These Petrochromis morphs share mitochondrial haplotypes, yet microsatellite loci reveal that their sympatric populations form distinct genetic groups. Nuclear divergence between the two morphs is equivalent to that which arises geographically within one of the morphs over short distances, and is substantially smaller than that among other sympatric species in this genus. These patterns suggest that these morphs diverged only recently, yet that barriers to gene flow exist which prevent extensive admixture despite their sympatric distribution. The morphs studied here provide an unusual example of active diversification in Lake Tanganyika's generally ancient cichlid fauna and enable comparisons of speciation processes between Lake Tanganyika and other African lakes.