Patterns of differentiation in the life history and demography of four recently described species of the Brachionus calyciflorus cryptic species complex

Wei Zhang,Libin Zhou,Steven A J Declerck,Kimberley D Lemmen,Spiros Papakostas

doi:10.1111/fwb.13388

Wei Zhang, Libin Zhou + Show 3 more

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https://doi.org/10.1111/fwb.13388

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Abstract

Abstract Brachionus calyciflorus is arguably the most studied freshwater monogonont rotifer. Although it has been recognised as a cryptic species complex for more than a decade, a formal (re‐)description of the four species known so far (B. calyciflorus, Brachionus dorcas, Brachionus elevatus, and Brachionus fernandoi) has only recently been made. Information on the ecology of these species is very scant and fragmented. The aim of this study was to test for ecological divergence between these four species, specifically their life history strategy and population demography. We conducted a life history experiment using 12–16 genotypes per species. For each species, genotypes were extracted from at least three different natural populations. In addition, we performed population‐level culture experiments with the aim to compare population growth rates and demographic structure of experimental populations among species. Finally, we searched the literature for life history studies with molecular data allowing retrospective species identification. We found pronounced differences in life history traits between B. fernandoi and the other three species. B. fernandoi had higher egg and juvenile development times and a lower egg production rate and mictic ratio. We detected no significant life history differences among B. calyciflorus, B. elevatus, and B. dorcas. Population growth rates of B. fernandoi and B. calyciflorus were higher than those of B. elevatus and B. dorcas. Life history divergence resulted in marked differences in the demographic structure of populations. Populations of B. fernandoi contained larger fractions of pre‐reproductive females and lower fractions of adult females with sexual eggs than populations of B. calyciflorus, B. elevatus, and B. dorcas. Mortality was found to be highest in B. elevatus and lowest in B. calyciflorus populations. Our results show that a reverse taxonomy approach is powerful in revealing sources of variation in ecologically relevant traits of cryptic species, such as life history and demographic structure. Explicit consideration of this variation is crucial for future studies of their dynamics in natural communities.

Highlights

Cryptic species are two or more morphologically similar species under one species name (Bickford et al, 2007)
Using genotypes collected from one single population, they found that B. dorcas, B. calyciflorus, and B. fernandoi showed different responses in their mictic ratio and population growth rates to varia‐ tion in temperature and food concentrations
Our results demonstrate the existence of substantial life history di‐ vergences among the species described by Michaloudi et al (2018) and illustrate its potential implications for population demography

Summary

| INTRODUCTION

Cryptic species are two or more morphologically similar species under one species name (Bickford et al, 2007). Genetic diver‐ gence among populations within species may result from drift or adaptation to local (Campillo, García‐Roger, Carmona, & Serra, 2011; De Meester, Gómez, Okamura, & Schwenk, 2002; Declerck et al, 2015) or regional conditions (Ma et al, 2010) Such genetic differences potentially bias comparisons among species if based on one or just a few genotypes or populations. The aims of the present study were: (1) to provide a compre‐ hensive comparison for the existence of systematic life history divergences among the four cryptic species described for the B. caly‐ ciflorus complex by Michaloudi et al (2018); and (2) to illustrate the potential impact of such differences for population growth rate and demography. We searched the literature for life history stud‐ ies comparing phylogenetically divergent clades of the B. calyciflorus species complex and traced these clades back to the four species described by Michaloudi et al (2018) using the molecular informa‐ tion provided by these studies

| METHODS

| Literature survey

Findings

| DISCUSSION