Pelagic–benthic resource polymorphism in <i>Schizopygopsis thermalis</i> Herzenstein 1891 (Pisces, Cyprinidae) in a headwater lake in the Salween River system on the Tibetan Plateau

Qiao, Jialing; Hu, Jiaxin; Qin, Xia; Zhu, Ren; Chen, Kang; Zhao, Jie; Yan, Yunzhi; Chu, Ling; He, Dekui

doi:10.1002/ece3.6470

Cited by 6 publications

(2 citation statements)

References 47 publications

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“…Yet, patterns of convergence in previous studies are also broadly apparent [36,37]. Additionally, the rapid formation of multiple independent 'species flocks' has occurred within unique and isolated alpine lake habitat [38][39][40][41][42], with an emerging consensus indicating recurrent ecotypic formation along riverine gradients [38,43]. Here, two Himalayan species are of particular interest: Schizothorax progastus and S. richardsonii.…”

Section: (B) a Case Study Involving Schizothoraxmentioning

confidence: 98%

Parallel introgression, not recurrent emergence, explains apparent elevational ecotypes of polyploid Himalayan snowtrout

Chafin

Regmi

et al. 2021

Preprint

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Replicated evolutionary patterns are often attributed to recurrent emergence following parallel selective pressures. However, similar genetic patterns (e.g., 'genomic islands') can also emerge following extensive homogenization in secondary contact, as a by-product of heterogeneous introgression. For example, within Himalayan tributaries of the Ganges/Brahmaputra rivers, drainage-specific mtDNA clades of polyploid snowtrout (Cyprinidae: Schizothorax) are partitioned as co-occurring morphological 'ecotypes,' hypothesized to represent parallel divergence among adjacent streams. To evaluate this scenario, we utilized a reduced-representation genomic approach (N=35,319 de-novo and N=10,884 transcriptome-aligned SNPs) applied to high-altitude Nepali/Bhutanese snowtrout (N=48 each). We unambiguously quantified ploidy levels by first deriving genome-wide allelic depths followed by ploidy-aware Bayesian models that produced genotypes statistically consistent with diploid/tetraploid expectations. When genotyped SNPs were clustering within drainages, the convergence of eco-phenotypes was sustained. However, subsequent partitioned analyses of phylogeny and population admixture instead identified subsets of loci under selection which retained genealogical concordance with morphology, with apparent patterns of parallel ecotype emergence instead driven by widespread genomic homogenization. Here, prior isolation is effectively masked by admixture occurring in secondary contact. We note two salient factors:1) Polyploidy has promoted homogenization in tetraploid Himalayan snowtrout; and 2) Homogenization varies across Himalayan tributaries, presumably in lockstep with extent of anthropogenic modification.

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Section: (B) a Case Study Involving Schizothoraxmentioning

confidence: 98%

Parallel introgression, not recurrent emergence, explains apparent elevational ecotypes of polyploid Himalayan snowtrout

Chafin

Regmi

et al. 2021

Preprint

View full text Add to dashboard Cite

show abstract

“…Yet, in previous studies, patterns of convergence are also broadly apparent [49,50]. Additionally, the rapid formation of multiple 'species flocks' has occurred within unique and isolated alpine lake habitats [51][52][53][54][55], with recurrent divergences as an emerging consensus [51,56]. Here, two Himalayan species are of particular interest: Schizothorax progastus and S. richardsonii.…”

Section: A Case Study Involving Schizothoraxmentioning

confidence: 99%

Parallel introgression, not recurrent emergence, explains apparent elevational ecotypes of polyploid Himalayan snowtrout

et al. 2021

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The recurrence of similar evolutionary patterns within different habitats often reflects parallel selective pressures acting upon either standing or independently occurring genetic variation to produce a convergence of phenotypes. This interpretation (i.e. parallel divergences within adjacent streams) has been hypothesized for drainage-specific morphological ‘ecotypes’ observed in polyploid snowtrout (Cyprinidae: Schizothorax ). However, parallel patterns of differential introgression during secondary contact are a viable alternative hypothesis. Here, we used ddRADseq ( N = 35 319 de novo and N = 10 884 transcriptome-aligned SNPs), as derived from Nepali/Bhutanese samples ( N = 48 each), to test these competing hypotheses. We first employed genome-wide allelic depths to derive appropriate ploidy models, then a Bayesian approach to yield genotypes statistically consistent under the inferred expectations. Elevational ‘ecotypes’ were consistent in geometric morphometric space, but with phylogenetic relationships at the drainage level, sustaining a hypothesis of independent emergence. However, partitioned analyses of phylogeny and admixture identified subsets of loci under selection that retained genealogical concordance with morphology, suggesting instead that apparent patterns of morphological/phylogenetic discordance are driven by widespread genomic homogenization. Here, admixture occurring in secondary contact effectively ‘masks’ previous isolation. Our results underscore two salient factors: (i) morphological adaptations are retained despite hybridization and (ii) the degree of admixture varies across tributaries, presumably concomitant with underlying environmental or anthropogenic factors.

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Trophic resource partitioning by sympatric ecomorphs of Schizopygopsis (Cyprinidae) in a young Pamir Mountain lake: preliminary results

2020

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Pelagic–benthic resource polymorphism in Schizopygopsis thermalis Herzenstein 1891 (Pisces, Cyprinidae) in a headwater lake in the Salween River system on the Tibetan Plateau

Cited by 6 publications

References 47 publications

Parallel introgression, not recurrent emergence, explains apparent elevational ecotypes of polyploid Himalayan snowtrout

Parallel introgression, not recurrent emergence, explains apparent elevational ecotypes of polyploid Himalayan snowtrout

Parallel introgression, not recurrent emergence, explains apparent elevational ecotypes of polyploid Himalayan snowtrout

Trophic resource partitioning by sympatric ecomorphs of Schizopygopsis (Cyprinidae) in a young Pamir Mountain lake: preliminary results

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