Morphological variation associated with trophic niche expansion within a lake population of a benthic fish

Abstract

Ecological theory suggests that generalist species should have traits with multiple adaptive peaks. Consequently, in heterogeneous environments such adaptive landscapes may lead to phenotypic divergence that becomes fixed in populations via reproductive isolation, thus driving speciation. However, contrary to this expectation, the process of ecological diversification in wild populations is not always associated with obvious trait divergence and reproductive isolation due to some ecological and geographic constrains. To examine the ecological conditions that promote (or inhibit) divergence is quite important to improve our understanding of the underlying mechanisms. Here we examine how the patterns of trait variation (divergence/non-divergence) are determined in relation to ecological niche expansion and gene flow using a benthic fish, Pseudogobio esocinus, in the Lake Biwa system, Japan. The fish exhibited various patterns of morphological variation in mouth parts among populations. Lake fish tended to have a smaller mouth compared with river fish and also showed remarkable individual variations within some local samples. Lake fish utilized chironomid larvae as the primary prey, as in riverine fish. But, fish with smaller and narrower mouths utilized significantly higher proportions of amphipods (a novel prey unique to the lake) as their secondary prey. Microsatellite analysis detected no genetic structuring in the Lake Biwa catchment, suggesting no reproductive separation among eco-morphologically divergent individuals. Our results exemplify population niche expansion associated with continuous eco-morphological variation without divergence, and provide insights into the role of non-discrete diversification for thriving in heterogeneous environments.

DNA metabarcoding suggests adaptive seasonal variation of individual trophic traits in a critically endangered fish

“…According to the prevailing trophic niche theory, BIC rather than individual niche width (INW), is expected to drive trophic niche variation (Araújo et al, 2011 ; Bolnick et al, 2003 ; Sjödin et al, 2018 ). Most empirical studies conclude that BIC variation is driven by interindividual variation in prey preference, microhabitat specialization or individual variation in foraging behaviour (e.g., Endo & Watanabe, 2020 ; Lewis, 1986 ; Persson, 1985 ; Svanbäck & Bolnick, 2005 ). However, in our case, simulations revealed that the measured BIC in Z. asper did not significantly differ from the null hypothesis of random foraging (Figure 5 ), rejecting the hypothesis of individual specialization.…”

Samsun Bölgesi’nde Yaşayan Salmo Populasyonlarının Genetik ve Morfometrik Yapısının Belirlenmesi: Karadeniz Bölgesi için Yeni Bir Kayıt

“…Thus, phenotypic differences and similarities between different locations of the same species can be evaluated in future studies. It is a really important point to determine the phenotypic variation caused by environmental factors (Cadrin, 2000;Özpiçak & Polat, 2019;Endo & Watanabe, 2020;Dunn et al, 2020).…”

Vertical habitat preferences shape the fish gut microbiota in a shallow lake

“…In contrast, benthic bacterial communities appear to be more stable and less affected by seasonal shifts ( Zhong et al, 2022 ). Meanwhile, fish, which were important parts in lake ecosystems, show discrepant behavior among different water layers ( Endo and Watanabe, 2020 ; St. John et al, 2022 ). To the best of our knowledge, there have been no systematic studies of how water and sediments microbial communities in lakes affect the structure and function of gut microbes in fish with pelagic or benthic habitat preferences.…”