Correlating Early Evolution of Parasitic Platyhelminths to Gondwana Breakup

Abstract

Investigating patterns and processes of parasite diversification over ancient geological periods should involve comparisons of host and parasite phylogenies in a biogeographic context. It has been shown previously that the geographical distribution of host-specific parasites of sarcopterygians was guided, from Palaeozoic to Cainozoic times, mostly by evolution and diversification of their freshwater hosts. Here, we propose phylogenies of neobatrachian frogs and their specific parasites (Platyhelminthes, Monogenea) to investigate coevolutionary processes and historical biogeography of polystomes and further discuss all the possible assumptions that may account for the early evolution of these parasites. Phylogenetic analyses of concatenated rRNA nuclear genes (18S and partial 28S) supplemented by cophylogenetic and biogeographic vicariance analyses reveal four main parasite lineages that can be ascribed to centers of diversity, namely Australia, India, Africa, and South America. In addition, the relationships among these biogeographical monophyletic groups, substantiated by molecular dating, reflect sequential origins during the breakup of Gondwana. The Australian polystome lineage may have been isolated during the first stages of the breakup, whereas the Indian lineage would have arisen after the complete separation of western and eastern Gondwanan components. Next, polystomes would have codiverged with hyloid sensu stricto and ranoid frog lineages before the completion of South American and African plate separation. Ultimately, they would have undergone an extensive diversification in South America when their ancestral host families diversified. Therefore, the presence of polystome parasites in specific anuran host clades and in discrete geographic areas reveals the importance of biogeographic vicariance in diversification processes and supports the occurrence and radiation of amphibians over ancient and recent geological periods.

A time and space complexity reduction for coevolutionary analysis of trees generated under both a Yule and Uniform model

“…This set includes evolutionary data from a number of fields including but not limited to, pathogens and their hosts (Charleston and Robertson, 2002), plant-insect relationships (McLeish et al, 2007), the evolutionary dependencies between plants and fungi (Refrégier et al, 2008), parasitic (Page et al, 2004) and mutualistic (Jackson, 2004) coevolution, and biogeography (Badets et al, 2011). The aim of this data set is to ensure that the running time improvements offered by the newly proposed data structure are consistent across the full spectrum of coevolutionary instances.…”

Nematodes Associated With Mammals in the Great American Biotic Interchange (Gabi)

“…Nevertheless, determination of both the origin of host-parasite associations is possible by using indirect methods, which include the increase of taxon and geographic sampling and the calibration of molecular clocks enforcing switches in geographic distribution or association with hosts. With the use of ancillary geological evidence, it is possible to estimate the age of associations, especially in those cases that involve an evident shift in the geographic distribution that is linked to a dated geological event (Ricklefs & Outlaw 2010, Badets et al 2011, Outlaw &Ricklefs 2011. Thus, as in other organisms, the study of the evolution of parasites is possible through the analysis of their genetic structure (De Baets & Littlewood 2015), which again can be dated by correlating shifts in the distribution of parasites in their hosts or in new geographic areas.…”

Constraining the Deep Origin of Parasitic Flatworms and Host-Interactions with Fossil Evidence

“…Thus, a cophylogenetic approach has been used (Hafner et al, 1994;Page et al, 1998;Light and Hafner, 2007), which may in turn provide a robust evolutionary timescale for apparent cospeciating symbiotic species when the timescale of the host lineage is (comparably) well constrained (Moran et al, 1993(Moran et al, , 1995. Due to the lack of well-preserved specimens in parasitic flatworms, most molecular clock studies have relied on the host fossil record to inform divergence estimates (Verneau et al, 2002(Verneau et al, , 2009aOlson et al, 2010;Badets et al, 2011;Héritier et al, 2015). More rarely biogeography (focusing on vicariance events) has been invoked to constrain molecular clock estimates of parasitic flatworms Waltari et al, 2007;Badets et al, 2011;Martínez-Aquino et al, 2014).…”

“…Due to the lack of well-preserved specimens in parasitic flatworms, most molecular clock studies have relied on the host fossil record to inform divergence estimates (Verneau et al, 2002(Verneau et al, , 2009aOlson et al, 2010;Badets et al, 2011;Héritier et al, 2015). More rarely biogeography (focusing on vicariance events) has been invoked to constrain molecular clock estimates of parasitic flatworms Waltari et al, 2007;Badets et al, 2011;Martínez-Aquino et al, 2014). Only one study (Perkins, 2010) used the parasitic flatworm fossil record as a calibration, although it relied on the Upper Devonian and Carboniferous putative flatworm fossils, whose taxonomic assignment to Monogenea and Cestoda, respectively, is still debated (as discussed above).…”

“…Time constraints on the origin and evolution of parasitism in this group are still poorly resolved due to their patchy and largely overlooked fossil record (Littlewood and Donovan, 2003;Littlewood, 2006). The fossil record of parasitic flatworms is often disregarded by parasitologists (Combes, 2001;Littlewood, 2006;Verneau et al, 2009a;Badets et al, 2011) and evolutionary (paleo)biologists (Labandeira, 2002;Erwin et al, 2011;Wey-Fabrizius et al, 2013) alike. Most parasitologists have therefore focused on extrapolating or interpolating extant parasiteehost associations to infer information on the evolution history of parasitic flatworms (Llewellyn, 1987;Brooks, 1989;Brooks and McLennan, 1993;Boeger and Kritsky, 1997;Hoberg, 1999;Hoberg et al, 1999;Littlewood et al, 1999a).…”