Depth and substratum differentiations among coexisting herbivorous cichlids in Lake Tanganyika

Abstract

Cichlid fish in Lake Tanganyika represent a system of adaptive radiation in which eight ancestral lineages have diversified into hundreds of species through adaptation to various niches. However, Tanganyikan cichlids have been thought to be oversaturated, that is, the species number exceeds the number of niches and ecologically equivalent and competitively even species coexist. However, recent studies have shed light on niche segregation on a finer scale among apparently equivalent species. We observed depth and substratum preferences of 15 herbivorous cichlids from four ecomorphs (i.e. grazer, browser, scraper and scooper) on a rocky littoral slope for 14 years. Depth differentiation was detected among grazers that defended feeding territories and among browsers with feeding territories. Cichlid species having no feeding territory also showed specificity on depth and substratum, resulting in habitat segregation among species that belong to the same ecomorph. Phylogenetically close species did not occupy adjacent depths, nor the opposite depth zones. Our findings suggest that apparently equivalent species of the same ecomorph coexist parapatrically along depth on a few-metre scale, or coexist with different substratum preferences on the rocky shore, and this niche segregation may have been acquired by competition between encountering equivalent species through repetitive lake-level fluctuations.

The effects of land use disturbance vary with trophic position in littoral cichlid fish communities from Lake Tanganyika

“…While consumer effects on prey are well known, the role of consumer diversity in affecting community structure or ecosystems is not particularly well understood, although Burkepile and Hay (2008) demonstrated that herbivorous fish species richness is critical for preserving coral reefs. Herbivores also form an important component of communities in the African Great Lakes (Hata & Ochi, 2016), and their decline may have serious implications for these systems. For example, the decrease in diversity of Lake Victoria herbivorous haplochromine cichlids after the introduction of the Nile perch (Lates niloticus) could have led to trophic cascades in this ecosystem (Goldschmidt, Witte, & Wanink, 1993).…”

Segregación espacial y trófica entre el cíclido invasor Amatitlania nigrofasciata y el nativo Herichthys pantostictus en la Reserva de la Biosfera Barranca de Metztitlán, Hidalgo, México

“…En tanto que la segregación de nichos a través de la microdistribución diferencial de especies del género Haplocromis que se alimentan de "Aufwuchs" (perifiton), se asoció a la profundidad y otros parámetros topográficos en el lago Victoria (Seehausen y Bouton, 1997). También, en 15 especies herbívoras de 4 ecomorfos de alimentación en el lago Tangañica se detectó diferenciación en el uso de profundidad y sustrato entre las especies de un mismo ecomorfo (Hata y Ochi, 2016). Finalmente, en el Parque Nacional del Lago Malawi, la disposición de áreas de alimentación de la fauna que habitan los litorales rocosos sugiere segregación espacial, lo que potencialmente ha promovido la coexistencia entre las especies nativas e introducidas, ésto a más de 30 años de la introducción de estas últimas (Makocho y Stauffer, 2018).…”