Deep‐sea squat lobster biogeography (Munidopsidae: Leiogalathea) unveils Tethyan vicariance and evolutionary patterns shared by shallow‐water relatives

Abstract

The ecology, abundance and diversity of galatheoid squat lobsters make them an ideal group to study deep-sea diversification processes. Here, we reconstructed the evolutionary and biogeographic history of Leiogalathea, a genus of circum-tropical deep-sea squat lobsters, in order to compare patterns and processes that have affected shallow-water and deep-sea squat lobster species. We first built a multilocus phylogeny and a calibrated species tree with a relaxed clock using StarBEAST2 to reconstruct evolutionary relationships and divergence times among Leiogalathea species. We used BioGeoBEARS and a DEC model, implemented in RevBayes, to reconstruct ancestral distribution ranges and the biogeographic history of the genus.Our results showed that Leiogalathea is monophyletic and comprises four main lineages; morphological homogeneity is common within and between clades, except in one; the reconstructed ancestral range of the genus is in the Atlantic and Indian oceans (Tethys). They also revealed the divergence of the Atlantic species around 25 million years ago (Ma), intense cladogenesis 15-25 Ma and low levels of speciation over the last 5 million years (Myr). The four Leiogalathea lineages showed similar patterns of speciation: allopatric speciation followed by range expansion and subsequent stasis. Leiogalathea started diversifying during the Oligocene, likely in the Tethyan. The Atlantic lineage then split from its Indo-Pacific sister group due to vicariance driven by closure of the Tethys Seaway. The Atlantic lineage is less speciose compared with the Indo-Pacific lineages, with the Tropical Southwestern Pacific being the current centre of diversity. Leiogalathea diversification coincided with cladogenetic peaks in shallow-water genera, indicating that historical biogeographic events similarly shaped the diversification and distribution of both deep-sea and shallow-water squat lobsters.

Munidopsis geyeri and M. exuta (Crustacea: Munidopsidae): A study of two deep-sea, amphi-Atlantic species that co-occur in the southern Gulf of Mexico

“…The studies of bathyal galatheids of the Indo-Pacific region that compare Paramunida Baba, 1988 of Munididae and Leiogalathea Baba, 1969 of Munidopsidae Ortmann, 1898; support similar patterns of diversification to those described in shallow-water galatheids (Cabezas et al 2012;Rodríguez-Flores et al 2020). The morphological homogeneity, the low intraspecific divergences, and low phylogenetic support of some genera has been explained by a set of rapid radiation events that left no signs of evolutionary splitting or divergence of taxa, by stasis, or by constraints in its morphological evolution (Cabezas et al 2009;Machordom & Macpherson 2004).…”

Mitogenomic phylogeny of mud snails of the mostly Atlantic/Mediterranean genusTritia(Gastropoda: Nassariidae)

“…In fact, fragmentation of the Tethys Ocean has been suggested as the main driver of the disjunct, endemic and relict distributions of many Tethyan lineages (i.e. Ozawa et al., 2009; Rodríguez‐Flores et al., 2020). Accordingly, the puzzling phylogenetic position of the Australian and New Zealand endemic T. ephamilla , which diverged about 16 Mya from East Atlantic/ Mediterranean taxa (as well as the sister relationship of the Australian T. buchardi and the North‐west Atlantic I. obsoleta ; Galindo et al., 2016), would represent one of the latest split events prior to the closure.…”

Cenozoic Tethyan changes dominated Eurasian animal evolution and diversity patterns

“…The closure of the Tethys Sea erected physical barriers to the exchange of marine animals near the equator between the Atlantic and the Indo-West Pacific, promoting vicariant divergence. The divergence time and distribution patterns of many extant marine animals clearly reflect the impacts, such as deep-sea squat lobsters ( Rodríguez-Flores et al, 2020 ), intertidal talitrids ( Liu et al, 2018 ), seahorses ( Li et al, 2021 ), and other coral reef fishes ( Cowman & Bellwood, 2013 ). Data from fossil deposits, such as the significant decrease in the similarity between the Mediterranean and Pakistan gastropod faunas during the Early Miocene, also reflect vicariance ( Harzhauser et al, 2007 ).…”