Abstract
Abstract. How environmental change affects a species' phenotype is crucial not only for taxonomy and biodiversity assessments but also for its application as a palaeo-ecological and ecological indicator. Previous investigations addressing the impact of the climate and hydrochemical regime on ostracod valve morphology have yielded contrasting results. Frequently identified ecological factors influencing carapace shape are salinity, cation, sulfate concentrations, and alkalinity. Here, we present a thorough approach integrating data with the carapace outline and surface details of the ubiquitous Neotropical cytheroidean ostracod species Cytheridella ilosvayi, as well as several climatic and hydrochemical variables, in order to investigate a potential link between morphology and environmental conditions. A recent study previously demonstrated considerable biogeographical variation in valve morphology among Floridian, Mexican and Brazilian populations of this species. We hypothesize that the climatic differences between the regions it inhabits and associated differences in hydrochemical regimes have influenced valve morphology and eventually led to biogeographically distinctive groups. Generalized least-squares Procrustes analyses based on outline and structural features were applied to the left and right valves of adult females and males. The analyses identified relative carapace length and shape symmetry as most important morphological characteristics representing shape differences across all datasets. Two-block partial least-squares analyses and multiple regressions indicate strong relationships between morphological and environmental variables, specifically with temperature seasonality, annual precipitation and chloride and sulfate concentrations. We suggest that increased temperature seasonality slowed down growth rates during colder months, potentially triggering the development of shortened valves with well-developed brood pouches. Differences in chloride and sulfate concentrations, related to fluctuations in precipitation, are considered to affect valve development via controlling osmoregulation and carapace calcification. The factors identified by our analyses represent hitherto unknown drivers for ostracod ecophenotypy in other species and therefore suggest that environmental predictors for morphological variability are not consistent across non-marine ostracods.
Highlights
Understanding how species respond to environmental change is crucial for their application as proxies for past climate fluctuations as well as in forecasting the future dynamics and distributions of species
We apply a thorough approach integrating morphometric data from carapace outline and surface details, as well as several climatic and hydrochemical variables, in order to investigate a potential link between morphology and environmental conditions
As the variables measured per sampling station only provide a snapshot of the local ecological conditions, the set of variables was supplemented with bioclimatic data
Summary
Understanding how species respond to environmental change is crucial for their application as proxies for past climate fluctuations as well as in forecasting the future dynamics and distributions of species. Morphological diversity represents a key feature of the interpretation of faunal changes (Wagner and Erwin, 2006) and ecological shifts (Mahler et al, 2010) and prompts discussions about speciation and extinction processes over time (e.g. Ciampaglio, 2004). Differences in shape and size among species have been shown to relate to changes of environmental parameter, in particular, differences in temperature across various clades C. Wrozyna et al.: Significance of climate and hydrochemistry on shape variation response has been documented for a variety of species, both recent and fossil Wrozyna et al.: Significance of climate and hydrochemistry on shape variation response has been documented for a variety of species, both recent and fossil (e.g. Hellberg et al, 2001; Zieritz and Aldridge, 2009; Inoue et al, 2013; Neubauer et al, 2013; Clewing et al, 2015)
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