title: Sex and species specific isotopic niche specialisation increases with trophic complexity: evidence from an ephemeral pond ecosystem.
abstract: It is generally accepted that organisms that naturally exploit an ecosystem facilitate coexistence, at least partially, through resource partitioning. Resource availability is, however, highly variable in space and time and as such the extent of resource partitioning must be somewhat dependent on availability. Here we test aspects of resource partitioning at the inter- and intra-specific level, in relation to resource availability in an atypical aquatic environment using an isotope approach. Using closely related key organisms from an ephemeral pond, we test for differences in isotopic signatures between two species of copepod and between sexes within each species, in relation to heterogeneity of basal food resources over the course of the ponds hydroperiod. We show that basal food resource heterogeneity increases over time initially, and then decreases towards the end of the hydroperiod, reflective of the expected evolution of trophic complexity for these systems. Resource partitioning also varied between species and sexes, over the hydroperiod with intra- and inter-specific specialisation relating to resource availability. Intra-specific specialisation was particularly evident in the omnivorous copepod species. Our findings imply that trophic specialisation at both the intra- and inter-specific level is partly driven by basal food resource availability.
authors.affiliation: Zoology and Entomology, Rhodes University, Grahamstown, Eastern Cape, South Africa.
authors.forename: Tatenda
authors.initials: T
authors.lastname: Dalu
authors.affiliation: South African Institute for Aquatic Biodiversity, Grahamstown, Eastern Cape, South Africa.|School of Science, Monash University Malaysia, Jalan Lagoon Selatan, 47500 Bandar Sunway, Selangor Darul Ehsan, Malaysia.
authors.forename: Ryan J
authors.initials: RJ
authors.lastname: Wasserman
authors.affiliation: Department of Botany, Coastal and Marine Research Unit, Nelson Mandela Metropolitan University, P O Box 77000, Port Elizabeth 6031, South Africa.
authors.forename: Tim J F
authors.initials: TJ
authors.lastname: Vink
authors.affiliation: South African Institute for Aquatic Biodiversity, Grahamstown, Eastern Cape, South Africa.
authors.forename: Olaf L F
authors.initials: OL
authors.lastname: Weyl
mesh_terms: D000818:Animals; D002247:Carbon Isotopes; D033342:Copepoda / Q000502:physiology*; D017753:Ecosystem; D005247:Feeding Behavior; D005260:Female; D008297:Male; D061005:Ponds; D012727:Sex Characteristics; D013045:Species Specificity
chemical_list: D002247:Carbon Isotopes