cave shrimps of the Typhlatya genus are common and widespread in fresh, brackish and marine groundwater throughout the Yucatan peninsula (Mexico). these species are ideal models to test niche partitioning within sympatric species in...
morecave shrimps of the Typhlatya genus are common and widespread in fresh, brackish and marine groundwater throughout the Yucatan peninsula (Mexico). these species are ideal models to test niche partitioning within sympatric species in oligotrophic systems. nevertheless, their food sources remain unidentified, and despite their frequency and functional importance, distribution and abundance patterns of these species within caves have not been fully recognized. Here, we describe the abundance of three Typhlatya species in different temporal and spatial scales, investigate changes in water conditions, and potential sources of carbon as an indication of food origin. Species composition and abundance varied markedly in space and time revealing patterns that differed from one system to another and in relation to environmental parameters. isotope analysis showed that each species reflects a particular δ 13 C and Δ 14 C fingerprint, suggesting they feed in different proportions from the available carbon sources. Overall, our findings suggest a niche partitioning of habitat and feeding sources amongst the three Typhlatya species investigated, where environmental characteristics and physiological differences could play an important role governing their distribution patterns. The lack of photosynthesis in caves and the resulting limitation in food sources is one of the strongest selection pressures and drivers of evolution for life in caves 1. Competition for nutrients in oligotrophic environments, such as anchialine ecosystems-defined as subterranean estuaries that extend inland to the limit of seawater penetration 2 , certainly requires a unique set of specialization traits that allow for niche partitioning amongst stygobionts (aquatic species strictly bound to the subterranean habitat). A closer look at stygobiont biodiversity reveals that co-occurrence of sympatric species within the same system is rare but can be occasionally observed 3,4. This work gathers evidence that suggests how three sympatric cave shrimp species that coexist in groundwater ecosystems have partitioned their niche to avoid competitive exclusion. Groundwater in the anchialine systems of Yucatan is vertically stratified by the intrusion of marine water from the coast which inserts below the freshwater that constantly flows towards the coast 2. This marked halocline, along with changes in temperature, dissolved oxygen, pH and redox potential has been considered a physicochemical barrier that separates freshwater and saline communities 5,6. This stratification is expected in coastal systems, and as distance from the coast increases, the marine intrusion is found deeper and only a few deep cenotes inland may reach the saline layers 7. In terms of energy production and food webs, the sun-influenced cenote pools-cenote is a Mayan derived name for local sinkholes-are the only sites where photosynthesis can take place and allochthonous organic matter can enter the system. Therefore, these ecosystems have been historically regarded as dependent of open 1 Posgrado en Ciencias Biológicas, Unidad de Posgrado, Edificio A, 1er piso,
