Morphology mirrors trophic niche in a freshwater amphipod community

Abstract

1. Amphipod crustaceans are ubiquitous in temperate freshwaters, where they radiated multiple times in a broad range of habitats. This has led to significant morphological and ecological disparity. However, a limited knowledge of functional morphology and its relation to ecology has often led to the view that freshwater amphipods are omnivorous shredders. Herein, we hypothesise that trophic differentiation is related to functional morphology in a sympatric assemblage of three species belonging to three widespread families: Crangonyctidae, Gammaridae, and Niphargidae.2. We quantified seasonal diet composition by examining gut contents, and measured 42 functional morphological traits.3. Our results reveal a clear trophic and morphological differentiation among these sympatric species. The carnivorous Niphargus valachicus exhibited predatory traits exemplified by a smaller molar surface and stomach length, and larger/longer grasping, locomotory, and sensory appendages in comparison to the herbivorous Gammarus dacicus. The third species, Synurella ambulans, was omnivorous given its intermediate diet and morphology. We did not find consistent evidence for seasonal diet variation, except for the summer and winter diet of G. dacicus. 4. The observed niches stretched along a broad trophic spectrum, indicating that even small riverine amphipod communities can exhibit significant functional disparity.5. The apparent connection between morphology and diet is similar to that observed in other crustaceans, strengthening our mechanistic understanding of the nichemorphology link. However, the generality of these conclusions needs to be tested on larger species datasets.

Morphology, nuclearSNPsand mate selection reveal thatCOIbarcoding overestimates species diversity in a Mediterranean freshwater amphipod by an order of magnitude

“…The observed overall morphological similarity either supports true morphological crypsis or indicates that all studied individuals belong to the same species. As has already been shown for other amphipods, morphological traits accurately reflect occupied trophic niche (Copilaș-Ciocianu et al, 2021;Fi ser et al, 2013;Kralj-Fi ser et al, 2020;Premate et al, 2021) and therefore morphological similarity is likely to indicate the same ecological niche and similar use of available resources (Bock and Von Wahlert, 1965;Ricklefs and Miles, 1994). However, when considering individual traits separately, there was one significant difference in the stomach length between the males of MOTU S02 and S04 (mean K2P = 6.5%).…”

“…We examined morphological differentiation by measuring 49 traits that reflect diet, locomotion and reproduction (Copilaș‐Ciocianu et al., 2021; Fišer et al., 2013; Kralj‐Fišer et al., 2020; Premate et al., 2021) (Table S5). A complete description of landmarks and function of the examined traits is provided in Copilaș‐Ciocianu et al.…”

“…S5). A complete description of landmarks and function of the examined traits is provided in Copilaș-Ciocianu et al (2021). In total, we used 80 adult individuals (originating from precopulatory pairs, COI barcoded before the morphological analyses) from the four most common mitochondrial MOTUs (10 males and 10 females per MOTU; Table S2).…”

“…We examined morphological differentiation by measuring 49 traits that reflect diet, locomotion and reproduction(Copilaș- Ciocianu et al, 2021;Fi ser et al, 2013;Kralj-Fi ser et al, 2020;Premate et al, 2021) (Table…”