Coevolution With Host Fishes Shapes Parasitic Life Histories in a Group of Freshwater Mussels (Unionidae: Quadrulini).

Abstract

Ecological interactions among species often lead to parasitic lineages coevolving with host resources, which is often suggested as the primary driver of parasite diversification. Freshwater mussels are bivalves that possess a parasitic life cycle requiring larval encystment on freshwater vertebrates to complete metamorphosis. The North American freshwater mussel tribe Quadrulini has a suite of life history adaptations including highly specialized patterns of host use, infection strategies, and variable larval morphologies. However, the evolution of life histories has yet to be explored using phylogenetic comparative methods. In this study, we use a holistic approach incorporating biogeographical, ecological, molecular, and morphological datasets to reconstruct the evolution of Quadrulini. Comparative phylogenetic analyses suggested the diversification of Quadrulini has been driven, at least in part, by codiversification with their primary host fishes in Ictaluridae. Major diversification events in both ictalurids and quadrulines were estimated to have occurred in the Mississippi River basin throughout the Miocene. Life history characteristics associated with parasitism were supported to have coevolved with host repertories, supporting the hypothesis that ecological interactions with host fishes have shaped the evolution of highly specialized traits in this group. Our findings demonstrate the importance of ecological interactions with host resources in shaping the evolutionary history of freshwater mussels.

Using a Nested Sampling Design Across Spatial Scales to Gain Insights Into Distribution Patterns of Fishes, Mussels and Macroinvertebrates in a Riverine System

“…For instance, in the upper San Saba River, the species Pustulosa petrina , Pustulosa pustulosa (Neemuchwala et al. 2023, formerly named Cyclonaias petrina and C. pustulosa respectively), Tritogenia verrucosa and Amblema plicata only occurred at three sites in numbers >1 individual, but all those sites are riffles. Their prevalence in riffles can also be seen in the lower San Saba, where these species, particularly the Pustulosa species, were more abundant.…”

Mitochondrial sequence data reveal population structure within Pustulosa pustulosa

“…Pustulosa pustulosa sensu lato may comprise a single species based on phylogenetic delimitation methods ( Johnson et al, 2018 ; Neemuchwala et al, 2023 ), but within its extensive range distinct populations are associated with geography ( Lopes-Lima et al, 2019 ). Data from our study suggest that each previously recognized nominal species within P. pustulosa in Texas represent separate populations, which is supported by some morphological differences and geographic separation ( Lopes-Lima et al, 2019 ).…”

“…These analyses suggest each of these major regional groups have unique, albeit recent ( i.e ., after the Last Glacial Maximum, ~20,000 years ago), evolutionary trajectories and likely represent distinct ESUs. Therefore, assisted migration between regional groups should be avoided to prevent potentially disrupting adaptive gene complexes ( Allard, 1988 ) or narrow larval mussel (glochidia)-host fish associations ( Modesto et al, 2018 ; Neemuchwala et al, 2023 ). If assisted migration is warranted to augment overall population viability or mitigate local extirpations within RMUs, then management strategies should consider source populations that are within the RMU of the imperiled population(s).…”

“…Among recent taxonomic changes were the re-assignment of nine Quadrula (Rafinesque, 1820) species to the genus Cyclonaias ( Lopes-Lima et al, 2019 ; Williams et al, 2017 ), and more recently, several of those taxa were subsequently assigned to Pustulosa ( Neemuchwala et al, 2023 ). The focal species of this study, Pustulosa ( Cyclonaias ) pustulosa , has a wide latitudinal distribution ranging from southern Ontario, Canada to Texas, USA.…”

“…The focal species of this study, Pustulosa ( Cyclonaias ) pustulosa , has a wide latitudinal distribution ranging from southern Ontario, Canada to Texas, USA. Considerable phenotypic plasticity and intrinsic shell variation could be partly responsible for taxonomic confusion within and among species of Quadrula , Cyclonaias , and Pustulosa ( Campbell et al, 2005 ; Neemuchwala et al, 2023 ; Serb, Buhay & Lydeard, 2003 ). Some mussels occurring in different states of the USA (Texas, Louisiana, and Mississippi) are difficult to distinguish morphologically, and a recent revision at the species-level suggested synonymizing four species ( C. aurea , C. houstonensis , C. mortoni , and C. refulgens ) as C. pustulosa (currently P. pustulosa ) based on analysis of genetic and morphological data ( Johnson et al, 2018 ; Lopes-Lima et al, 2019 ); albeit, some weak associations between phylogenetic diversity and geography have also been detected by the same studies.…”