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Abstract Species delimitation is an imperative first step toward understanding Earth's biodiversity, yet what constitutes a species and the relative importance of the various processes by which new species arise continue to be debatable. Species delimitation in spiders has traditionally used morphological characters; however, certain mygalomorph spiders exhibit morphological homogeneity despite long periods of population‐level isolation, absence of gene flow, and consequent high degrees of molecular divergence. Studies have shown strong geographic structuring and significant genetic divergence among several species complexes within the trapdoor spider genusAptostichus, most of which are restricted to the California Floristic Province (CAFP) biodiversity hotspot. Specifically, theAptostichus icenogleicomplex, which comprises the three sibling species,A. barackobamai,A. isabella, andA. icenoglei, exhibits evidence of cryptic mitochondrial DNA diversity throughout their ranges in Northern, Central, and Southern California. Our study aimed to explicitly test species hypotheses within this assemblage by implementing a cohesion species‐based approach. We used genomic‐scale data (ultraconserved elements, UCEs) to first evaluate genetic exchangeability and then assessed ecological interchangeability of genetic lineages. Biogeographical analysis was used to assess the likelihood of dispersal versus vicariance events that may have influenced speciation pattern and process across the CAFP's complex geologic and topographic landscape. Considering the lack of congruence across data types and analyses, we take a more conservative approach by retaining species boundaries withinA. icenoglei.
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Delimiting the rare, endangered and actively speciating
Species delimitation is a contentious topic. The genomics revolution initially brought hope that identifying and classifying species would be easier through better methods and more data, but genomics has also brought complexity and controversy to delimitation. One solution can be to collect a larger sample of individuals at a finer geographic scale. But what if taxa are rare and collecting more samples is difficult or detrimental to the organisms at hand? In this issue ofMolecular Ecology Resources, Opatova et al. (2023) tackle the ambiguity of species delimitation in rare and endangered trapdoor spiders (genusCyclocosmia). The authors propose a framework for delimiting species when samples are hard to come by, such as in these rare and cryptic spiders. The authors combine extensive genomic sampling with statistical approaches that consider both the genetic distinctiveness of each population of spiders and how much gene flow occurs between these populations. Their proposed taxonomy balances two opposing signals, structure and gene flow, to count eight lineages ofCyclocosmia, and to point the way for future taxonomic studies of the rare or difficult to obtain.
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- Award ID(s):
- 1835893
- PAR ID:
- 10505649
- Publisher / Repository:
- Molecular Ecology Resources
- Date Published:
- Journal Name:
- Molecular Ecology Resources
- Volume:
- 24
- Issue:
- 3
- ISSN:
- 1755-098X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract The recognition and delineation of cryptic species remains a perplexing problem in systematics, evolution, and species delimitation. Once recognized as such, cryptic species complexes provide fertile ground for studying genetic divergence within the context of phenotypic and ecological divergence (or lack thereof). Herein we document the discovery of a new cryptic species of trapdoor spider,Promyrmekiaphila korematsuisp. nov. Using subgenomic data obtained via target enrichment, we document the phylogeography of the California endemic genusPromyrmekiaphilaand its constituent species, which also includesP. clathrataandP. winnemem. Based on these data we show a pattern of strong geographic structuring among populations but cannot entirely discount recent gene flow among populations that are parapatric, particularly for deeply diverged lineages withinP. clathrata. The genetic data, in addition to revealing a new undescribed species, also allude to a pattern of potential phenotypic differentiation where species likely come into close contact. Alternatively, phenotypic cohesion among genetically divergentP. clathratalineages suggests that some level of gene flow is ongoing or occurred in the recent past. Despite considerable field collection efforts over many years, additional sampling in potential zones of contact for both species and lineages is needed to completely resolve the dynamics of divergence inPromyrmekiaphilaat the population–species interface.more » « less
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1111/1755-0998.13938
