Island systems provide excellent arenas to test evolutionary hypotheses pertaining to gene flow and diversification of dispersal-limited organisms. Here we focus on an orbweaver spider genus
The Caribbean island biota is characterized by high levels of endemism, the result of an interplay between colonization opportunities on islands and effective oceanic barriers among them. A relatively small percentage of the biota is represented by ‘widespread species,’ presumably taxa for which oceanic barriers are ineffective. Few studies have explored in detail the genetic structure of widespread Caribbean taxa. The cobweb spider
- NSF-PAR ID:
- 10012366
- Publisher / Repository:
- PeerJ
- Date Published:
- Journal Name:
- PeerJ
- Volume:
- 3
- ISSN:
- 2167-8359
- Page Range / eLocation ID:
- e1422
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Cyrtognatha (Tetragnathidae) from the Caribbean, with the aims to reconstruct its evolutionary history, examine its biogeographic history in the archipelago, and to estimate the timing and route of Caribbean colonization. Specifically, we test ifCyrtognatha biogeographic history is consistent with an ancient vicariant scenario (the GAARlandia landbridge hypothesis) or overwater dispersal. We reconstructed a species level phylogeny based on one mitochondrial (COI) and one nuclear (28S) marker. We then used this topology to constrain a time-calibrated mtDNA phylogeny, for subsequent biogeographical analyses in BioGeoBEARS of over 100 originally sampledCyrtognatha individuals, using models with and without a founder event parameter. Our results suggest a radiation of CaribbeanCyrtognatha , containing 11 to 14 species that are exclusively single island endemics. Although biogeographic reconstructions cannot refute a vicariant origin of the Caribbean clade, possibly an artifact of sparse outgroup availability, they indicate timing of colonization that is much too recent for GAARlandia to have played a role. Instead, an overwater colonization to the Caribbean in mid-Miocene better explains the data. From Hispaniola,Cyrtognatha subsequently dispersed to, and diversified on, the other islands of the Greater, and Lesser Antilles. Within the constraints of our island system and data, a model that omits the founder event parameter from biogeographic analysis is less suitable than the equivalent model with a founder event. -
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Abstract Scorpions are an excellent system for understanding biogeographical patterns. Most major scorpion lineages predate modern landforms, making them suitable for testing hypotheses of vicariance and dispersal. The Caribbean islands are endowed with a rich and largely endemic scorpion fauna, the origins of which have not been previously investigated with modern biogeographical methods. Three sets of hypotheses have been proposed to explain present patterns of diversity in the Caribbean: (1) connections via land bridges, (2) vicariance events, and (3) overwater dispersal from continents and among islands. The present study investigates the biogeographical diversification of the New World buthid scorpion subfamily Centruroidinae Kraus, 1955, a clade of seven genera and more than 110 species; infers the ancestral distributions of these scorpions; and tests the relative roles of vicariance and dispersal in the formation of their present distributions. A fossil-calibrated molecular phylogeny was estimated with a Bayesian criterion to infer the dates of diversification events from which ancestral distributions were reconstructed, and the relative likelihood of models of vicariance vs. dispersal, calculated. Although both the timing of diversification and the ancestral distributions were congruent with the GAARlandia land-bridge hypothesis, there was no significant difference between distance-dependent models with or without the land-bridge.
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Premise Long‐distance dispersal has been important in explaining the present distributions of many plant species. Despite being infrequent, such dispersal events have considerable evolutionary consequences, because bottlenecks during colonization can result in reduced genetic diversity. We examined the phylogeographic history of
Lycium carolinianum , a widespread taxon that ranges from southeastern North America to several Pacific islands, with intraspecific diversity in sexual and mating systems.Methods We used Bayesian, likelihood, and coalescent approaches with nuclear and plastid sequence data and genome‐wide single nucleotide polymorphisms to reconstruct the dispersal history of this species. We also compared patterns of genetic variation in mainland and island populations using single nucleotide polymorphisms and allelic diversity at the
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Abstract Aim The “sexy shrimp”
Thor amboinensis is currently considered a single circumtropical species. However, the tropical oceans are partitioned by hard and soft barriers to dispersal, providing ample opportunity for allopatric speciation. Herein, we test the null hypothesis thatT. amboinensis is a single global species, reconstruct its global biogeographical history, and comment on population‐level patterns throughout the Tropical Western Atlantic.Location Coral reefs in all tropical oceans.
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Thor amboinensis were obtained through field collection and museum holdings. We used one mitochondrial (COI ) and two nuclear (NaK, enolase) gene fragments for global species delimitation and phylogenetic analyses (n = 83 individuals, 30 sample localities), while phylogeographical reconstruction in theTWA was based onCOI only (n = 303 individuals, 10 sample localities).Results We found evidence for at least five cryptic lineages (9%–22%
COI pairwise sequence divergence): four in the Indo‐West Pacific and one in the Tropical Western Atlantic. Phylogenetic reconstruction revealed that endemic lineages from Japan and the South Central Pacific are more closely related to the Tropical Western Atlantic lineage than to a co‐occurring lineage that is widespread throughout the Indo‐West Pacific. Concatenated and species tree phylogenetic analyses differ in the placement of an endemic Red Sea lineage and suggest alternate dispersal pathways into the Atlantic. Phylogeographical reconstruction throughout the Tropical Western Atlantic reveals little genetic structure over more than 3,000 km.Main conclusions Thor amboinensis is a species complex that has undergone a series of allopatric speciation events and whose members are in secondary contact in the Indo‐West Pacific. Nuclear‐ and mitochondrial‐ gene phylogenies show evidence of introgression between lineages inferred to have been separated more than 20 Ma. Phylogenetic discordance between multi‐locus analyses suggest thatT. amboinensis originated in the Tethys sea and dispersed into the Atlantic and Indo‐West Pacific through the Tethys seaway or, alternatively, originated in the Indo‐West Pacific and dispersed into the Atlantic around South Africa. Population‐level patterns in the Caribbean indicate extensive gene flow across the region.
