Differential response to heat stress among evolutionary lineages of an aquatic invertebrate species complex

Abstract

Under global warming scenarios, rising temperatures can constitute heat stress to which species may respond differentially. Within a described species, knowledge on cryptic diversity is of further relevance, as different lineages/cryptic species may respond differentially to environmental change. The Brachionus calyciflorus species complex (Rotifera), which was recently described using integrative taxonomy, is an essential component of aquatic ecosystems. Here, we tested the hypothesis that these (formerly cryptic) species differ in their heat tolerance. We assigned 47 clones with nuclear ITS1 (nuITS1) and mitochondrial COI (mtCOI) markers to evolutionary lineages, now named B. calyciflorus sensu stricto (s.s.) and B. fernandoi. We selected 15 representative clones and assessed their heat tolerance as a bi-dimensional phenotypic trait affected by both the intensity and duration of heat stress. We found two distinct groups, with B. calyciflorus s.s. clones having higher heat tolerance than the novel species B. fernandoi. This apparent temperature specialization among former cryptic species underscores the necessity of a sound species delimitation and assignment, when organismal responses to environmental changes are investigated.

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

“…Additional life history experiments suggested temperature as an important seasonal clue to these phenological differences by showing higher induction of mixis in B. fernandoi than in the other species at summer temperatures and the opposite pattern at autumn temperatures (Zhang et al., ). These results align well with the recent findings of Paraskevopoulou, Tiedemann, and Weithoff () who demonstrated a consistently higher tolerance to heat stress in B. calyciflorus than in B. fernandoi .…”

Temperature-dependent life history and transcriptomic responses in heat-tolerant versus heat-sensitive Brachionus rotifers

“…Both species generally exhibit a non-overlapping seasonal occurrence during summer and winter respectively, however, in November they co-occurred with B. fernandoi outnumbering B. calyciflorus s.s. in abundance 7 . Our previous comparative laboratory study on heat tolerance between different clones belonging to B. calyciflorus s.s. and B. fernandoi species has shown higher heat-tolerance of the former as compared to the latter 23 . In this study, acute heat-stress was imposed and the Critical Thermal Maximum (CT max ) was estimated as a proxy for survival.…”

Estimating Parameters From Multiple Time Series of Population Dynamics Using Bayesian Inference

“…From these we selected a subset of 13 experiments, which were replicates in the sense that the same species were used at the same inflow nutrient concentration and dilution rate, and daily counts of prey and predators are available. The experiments were conducted with a metazoan predator, the rotifer Brachionus calyciflorus s.s. (Michaloudi et al, 2018;Paraskevopoulou et al, 2018), and its prey Monoraphidium minutum, a unicellular green alga. The algae grew on nitrogen-limited medium.…”