Trophic differentiation and functional morphology of Niphargus (Amphipoda: Niphargus)

Premate, Ester (author), Fišer, Cene (mentor), Laurent, Simon (comentor)

The amphipod genus Niphargus is ecologically diverse, living in virtually all types of subterranean aquatic habitats. On a local scale, different Niphargus species regularly co-occur. The co-occurring species often differ in microhabitat preferences and morphology, suggesting that these species evolved different ecological niches. We focused on trophic niche differentiation of species occurring within the same community and aimed to identify possible links between selected morphological functional traits and trophic ecology. Previous studies suggested that Niphargus can feed on various food sources and use different feeding strategies, including detritivory, scavenging, and predation. Appendages involved into feeding, i.e. gnathopods, show a substantial between-species variation, suggesting that appendage morphology might correlate with feeding ecology. We sampled five caves and two interstitial sites, where at least two species of Niphargus co-occur. We measured carbon (C) and nitrogen (N) stable isotope ratios of animals and basal food resources, and estimated species’ trophic position. Besides that, we performed correlation analyses between morphological and isotopic data for cave species. The results imply that co-occurring species differ in their trophic ecology in all sampled communities. They differentiate either along δ15N, δ13C, or both, and occupy trophic positions ranging from 2.0 (detritivores) to 4.0 (secondary-level predators). In cave species, gnathopod size positively correlates with trophic position, while gnathopod shape negatively correlates with normalized δ13C values. Put together, our results suggest that trophic differentiation may operate as a mechanism mediating species coexistence within subterranean habitats, and that gnathopod size and shape are morphological functional traits which can be used to predict Niphargus’ trophic ecology.

• Language: English
• Keywords: trophic differentiation, functional traits, Niphargus, subterranean communities, ecological niche, coexistence
• Work type: Master's thesis/paper
• Organization: BF - Biotechnical Faculty
• Year: 2020
• PID: 20.500.12556/RUL-119704
• COBISS.SI-ID: 28188675
• Publication date in RUL: 11.09.2020

Secondary language

• Language: Slovenian
• Title: Trofična diferenciacija in funkcionalna morfologija slepih postranic (Amphipoda: Niphargus)

Abstract

Slepe postranice iz rodu Niphargus so ekološko pestra skupina, ki naseljuje različne tipe podzemnih vodnih habitatov. Različne vrste slepih postranic na lokalni ravni redno sobivajo. Sobivajoče vrste se med seboj pogosto razlikujejo v izbiri mikrohabitatov in morfologiji, kar kaže na razlike v njihovih ekoloških nišah. V nalogi smo se osredotočili na diferenciacijo trofičnih niš pri sobivajočih vrstah ter na možne povezave med trofično ekologijo in izbranimi morfološkimi lastnostmi. Pretekle študije so pokazale, da se slepe postranice prehranjujejo z različnimi viri hrane in uporabljajo različne prehranske strategije. Prehranjujejo se lahko kot detritivori, mrhovinarji, ali plenilci. Okončine, ki jih uporabljajo pri prehranjevanju (gnatopodi) se med vrstami znatno razlikujejo, zato smo predvidevali, da morfologija teh okončin korelira s trofično ekologijo. Vzorčili smo v petih jamah in na dveh intersticijskih mestih, kjer je znano, da sobivata najmanj dve vrsti slepih postranic. Izmerili smo razmerja stabilnih izotopov ogljika (C) in dušika (N) pri živalih in temeljnih prehranskih virih ter ocenili trofični nivo posameznih vrst. Poleg tega smo izvedli korelacijske analize med morfološkimi in izotopskimi podatki pri jamskih vrstah. Rezultati kažejo, da se sobivajoče vrste razlikujejo v trofični ekologiji v vseh vzorčenih združbah. Razlikujejo se v δ15N, δ13C, ali v obeh, in zasedajo trofične nivoje od 2. (detritivori) do 4. (plenilci drugega reda). Pri jamskih vrstah velikost gnatopoda pozitivno korelira s trofičnim nivojem, oblika gnatopoda pa negativno korelira z normaliziranimi vrednostmi δ13C. Na podlagi rezultatov zaključimo, I) da je trofična diferenciacija lahko eden izmed mehanizmov, vpletenih v sobivanje vrst tudi v podzemnih habitatih, in II) da sta velikost in oblika gnatopodov morfološki lastnosti, ki ju lahko uporabimo za napoved trofične ekologije vrst slepih postranic.

• Keywords: trofična diferenciacija, funkcionalne lastnosti, Niphargus, podzemne združbe, ekološka niša, sobivanje vrst