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ABSTRACT AimThuridillaBergh, 1872, is a lineage of herbivorous sea slugs externally distinguished by bright colours and distinctive patterns of lines and spots. Recent work revealed an exceptionally rapid, cryptic radiation of 13 species in the Indo‐Pacific, raising questions about mechanisms of speciation in this group. Here, we (i) study the diversification and historical biogeography ofThuridillain a phylogenetic context and (ii) assess the role of dispersal and vicariance as the predominant mode of speciation in the genus. LocationTropical and temperate regions of the Atlantic and Indo‐Pacific. Major Taxa StudiesGastropoda, Sacoglossa. MethodsA nearly complete taxon set with 28 out of 32 recognised species ofThuridillawas used, in a total sample of 172 specimens, together with sacoglossan outgroups. Phylogenetic relationships were determined using a multi‐locus approach combining two mitochondrial (COI and 16S) and one nuclear gene (H3). Species relationships, diversification times, and ancestral geographical ranges were inferred using relaxed‐clock methods together with Bayesian discrete phylogeographic methods under three calibration scenarios using the oldest known fossil of Sacoglossa,Berthelinia elegansCrosse, 1875, and tectonic events. ResultsThuridillaspecies branched off into four major clades in all calibration scenarios: two groups from the Atlantic plus Indo‐West Pacific (5 and 6 species) and two clades from the Indo‐West Pacific (4 and 17 species). The highest diversity of the genus is in the Western Pacific (14 spp.) with a peak in the East Indies Triangle (18 spp.), whereas the Atlantic is depauperate with only four species occurring in this ocean basin. Divergence between Atlantic and Indo‐West Pacific lineages occurred in two main temporal periods: the Miocene and the Pliocene. Speciation events within the 13 cryptic species‐complex fell mostly within Plio‐Pleistocene times. Main ConclusionsThe best supported hypothesis was an Indo‐West Pacific origin ofThuridillabetween 28 and 18 Mya during the Early Miocene. In the western Pacific, speciation likely occurred during transient allopatry during Plio‐Pleistocene sea‐level fluctuations. Under the three tested calibration scenarios, the limited diversity of the Atlantic Ocean is hypothesized to be derived from Miocene vicariant events associated with the closure of the Tethys Sea, dispersal across southern Africa, or long‐distance dispersal across the East Pacific Barrier prior to the uplift of the Isthmus of Panama.Thuridillais absent in the Eastern Pacific, potentially resulting from the extinction of ancestral lineages following the uplift of the Isthmus of Panama. Near‐complete sampling of diversity and reconstruction of historical biogeography thus yielded new insight into the relative contributions of dispersal versus vicariance during speciation over the history of this widely distributed, colourful genus.
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Phylogenomics Resolves the Relationships within Antennaria (Asteraceae, Gnaphalieae) and Yields New Insights into its Morphological Character Evolution and Biogeography
Abstract— Antennaria are dioecious perennial herbs distributed mainly in the Holarctic Region, with their major center of diversity in the Rocky Mountains of Western North America. The genus comprises 33 known sexual diploid/tetraploid species and at least five polyploid agamic complexes which mostly reproduce by forming asexual seeds. We performed a phylogenetic reconstruction of the 31 sexually-reproducing Antennaria species using a novel target enrichment method that employs custom capture probes designed to work across Asteraceae. Both concatenated and coalescent-based analyses of DNA sequence data from hundreds of nuclear loci recovered Antennaria as a monophyletic group except for the long-disputed species, Antennaria linearifolia , which was recovered outside of the genus. Antennaria was further resolved into three distinct, major lineages. Analysis of ancestral state reconstruction of 12 taxonomically important morphological characters elucidated patterns of character evolution throughout the genus. Estimations of ancestral geographic ranges and molecular dating analyses demonstrated the Rocky Mountain region, including the Vancouverian Province, as the center of origin for the genus Antennaria, around 5.8 MYA. Subsequent dispersals of Antennaria into the Arctic and Appalachian provinces, Canadian provinces, and Eurasia took place roughly 3.2 MYA, 2.4 MYA, and 1.6 MYA, respectively. Biogeographical stochastic mapping indicated that 51.4% of biogeographical events were based on within-area speciation. The remaining 48.6% of the events were divided into two types of dispersals: 1) range expansion dispersals (anagenic, 37%), and 2) founder/jump dispersals (cladogenic, 11.6%). Our results provide a framework for future evolutionary studies of Antennaria, including speciation, origin(s) of polyploidy, and agamospermy in the genus.
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- Award ID(s):
- 1745197
- PAR ID:
- 10164790
- Date Published:
- Journal Name:
- Systematic Botany
- Volume:
- 45
- Issue:
- 2
- ISSN:
- 0363-6445
- Page Range / eLocation ID:
- 387 to 402
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1600/036364420X15862837791221
