Phenotypic plasticity of life-history traits of a calanoid copepod in a tropical lake: Is the magnitude of thermal plasticity related to thermal variability?

Abstract

According to the Climatic Variability Hypothesis [CVH], thermal plasticity should be wider in organisms from temperate environments, but is unlikely to occur in tropical latitudes where temperature fluctuations are narrow. In copepods, food availability has been suggested as the main driver of phenotypic variability in adult size if the range of temperature change is less than 14°C. Leptodiaptomus garciai is a calanoid copepod inhabiting Lake Alchichica, a monomictic, tropical lake in Mexico that experiences regular, narrow temperature fluctuations but wide changes in phytoplankton availability. We investigated whether the seasonal fluctuations of temperature and food produce phenotypic variation in the life-history traits of this tropical species. We sampled L. garciai throughout a year and measured female size, egg size and number, and hatching success, along with temperature and phytoplankton biomass. The amplitude of the plastic responses was estimated with the Phenotypic Plasticity Index. This index was also computed for a published dataset of 84 copepod populations to look if there is a relationship between the amplitude of the phenotypic plasticity of adult size and seasonal change in temperature. The temperature annual range in Lake Alchichica was 3.2°C, whereas phytoplankton abundance varied 17-fold. A strong pattern of thermal plasticity in egg size and adult female size followed the inverse relationship with temperature commonly observed in temperate environments, although its adaptive value was not demonstrated. Egg number, relative reproductive effort and number of nauplii per female were clearly plastic to food availability, allowing organisms to increase their fitness. When comparing copepod species from different latitudes, we found that the magnitude of thermal plasticity of adult size is not related to the range of temperature variation; furthermore, thermal plasticity exists even in environments of limited temperature variation, where the response is more intense compared to temperate populations.

Indicatiewaarden van aquatische organismen

“…Het bestaan van nicheconstantie en -plasticiteit betekent dat databases met soortkenmerken opgebouwd uit gegevens afkomstig van grote biogeografische en klimatologische gebieden, zoals de freshwaterecology.info-database (http://www.freshwaterecology.info; Schmidt-Kloiber & Hering 2015) met voorzichtigheid moeten worden geïnterpreteerd (Mbaka et al 2015, Hamilton et al 2020. Dergelijke databases houden namelijk geen rekening met de grote plasticiteit in aanpassingen die sommige soorten kennen (Ortega-Mayagoitia et al 2018).…”

Limitations of trait‐based approaches for stressor assessment: The case of freshwater invertebrates and climate drivers

“…Trait information derived from field observations of the occurrence of taxa can cut across multiple environments, climates, and geographic regions (Schmidt‐Kloiber & Hering, ). Species display trait plasticity that can include adaptations to regional conditions, which complicate trait–environmental relationships (Ortega‐Mayagoitia, Hernandez‐Martinez, & Ciros‐Perez, ). As a result, trait values may not be generalizable across geographic areas (Mbaka, Szöcs, & Schäfer, ).…”

Plasticity is a locally adapted trait with consequences for ecological dynamics in novel environments

“…Plasticity in traits associated with life histories, such as reproductive output, body size, and somatic growth, has been linked not only to individual fitness (Acasuso‐Rivero et al., 2019 ) but also to population level persistence and dynamics (Ashander et al., 2016 ; Chevin & Lande, 2011 ; Fischer et al., 2014 ). The magnitude of environmental variation affects the prevalence of genotypes that express plasticity in reproductive and growth‐related traits, such as in calanoid copepods (Ortega‐Mayagoitia et al., 2018 ; Sereda et al., 2014 ) or Drosophila sp. (Manenti et al., 2015 ).…”