title: Linking stream ecology with morphological variability in a native freshwater fish from semi-arid Australia.
abstract: Environmental variation is a potent force affecting phenotypic expression. While freshwater fishes have provided a compelling example of the link between the environment and phenotypic diversity, few studies have been conducted with arid-zone fishes, particularly those that occur in geographically isolated regions where species typically inhabit intermittent and ephemeral creeks. We investigated morphological variation of a freshwater fish (the western rainbowfish, Melanotaenia australis) inhabiting creeks in the Pilbara region of northwest Australia to determine whether body shape variation correlated with local environmental characteristics, including water velocity, habitat complexity, predator presence, and food availability. We expected that the geographic isolation of creeks within this arid region would result in habitat-specific morphological specializations. We used landmark-based geometric morphometrics to quantify the level of morphological variability in fish captured from 14 locations within three distinct subcatchments of a major river system. Western rainbowfish exhibited a range of morphologies, with variation in body depth accounting for a significant proportion (>42%) of the total variance in shape. Sexual dimorphism was also apparent, with males displaying deeper bodies than females. While the measured local habitat characteristics explained little of the observed morphological variation, fish displayed significant morphological differentiation at the level of the subcatchment. Local adaptation may partly explain the geographic patterns of body shape variation, but fine-scale genetic studies are required to disentangle the effects of genetic differentiation from environmentally determined phenotypic plasticity in body shape. Developing a better understanding of environment-phenotype relationships in species from arid regions will provide important insights into ecological and evolutionary processes in these unique and understudied habitats.
authors.affiliation: School of Animal Biology (M092), The University of Western Australia 35 Stirling Highway, Crawley, Western Australia, 6009, Australia ; Ecosystems Research Group and West Australian Biogeochemistry Centre, School of Plant Biology, The University of Western Australia 35 Stirling Highway, Crawley, Western Australia, 6009, Australia.
authors.forename: Samantha
authors.initials: S
authors.lastname: Lostrom
authors.affiliation: School of Animal Biology (M092), The University of Western Australia 35 Stirling Highway, Crawley, Western Australia, 6009, Australia.
authors.forename: Jonathan P
authors.initials: JP
authors.lastname: Evans
authors.affiliation: Ecosystems Research Group and West Australian Biogeochemistry Centre, School of Plant Biology, The University of Western Australia 35 Stirling Highway, Crawley, Western Australia, 6009, Australia.
authors.forename: Pauline F
authors.initials: PF
authors.lastname: Grierson
authors.affiliation: School of Animal Biology (M092), The University of Western Australia 35 Stirling Highway, Crawley, Western Australia, 6009, Australia ; UWA Oceans Institute (M470), The University of Western Australia 35 Stirling Highway, Crawley, Western Australia, 6009, Australia.
authors.forename: Shaun P
authors.initials: SP
authors.lastname: Collin
authors.affiliation: Centre of Excellence in Natural Resource Management, The University of Western Australia Albany, Western Australia, Australia.
authors.forename: Peter M
authors.initials: PM
authors.lastname: Davies
authors.affiliation: School of Animal Biology (M092), The University of Western Australia 35 Stirling Highway, Crawley, Western Australia, 6009, Australia ; Ecosystems Research Group and West Australian Biogeochemistry Centre, School of Plant Biology, The University of Western Australia 35 Stirling Highway, Crawley, Western Australia, 6009, Australia.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Kelley
keywords: Local adaptation; Pilbara; phenotype–environment correlation; phenotypic plasticity; polymorphism; population differentiation