Importance of seagrass vegetation for habitat partitioning between closely related species, mobile macrofauna Neomysis (Misidacea)

Abstract

Seagrass meadows provide both habitats and a range of food sources for macrofaunal communities. These functions facilitate the coexistence of less mobile invertebrates (in comparison with mysids, such as amphipods) that are associated with seagrass leaves, and may also enhance the coexistence of highly mobile invertebrates such as mysid. We investigated the function of seagrass in supporting the coexistence of two mysid species, Neomysis awatschensis and N. mirabilis. These taxa are dominant in seagrass ecosystems of temperate coastal areas. We compared patterns of habitat use between the two species at mesoscales (among seagrass patches) and microscales (among seagrass leaves) by performing field surveys and laboratory experiments. The field survey results showed positive correlations in the abundance of the two mysid species, indicating that both species select similar habitats at the mesoscale level. In the laboratory experiments, the pattern of microhabitat selection (fundamental habitat) was similar for both species, even at increased densities and with the presence of an immobile habitatcompetitor (the gastropod Barleeia angustata) on the leaves. However, this pattern changed significantly when a food source (epiphytic microalgae) was present on the leaves. This result indicates that (i) inter-and intraspecific interference competition does not affect microhabitat selection in these two mysids and (ii) both Neomysis species use similar habitats at the feeding stage. Although these two closely related mysids species may have similar requirements for microhabitat and food, the evidence that they did not act as competitors is attributable to unrestricted microhabitat and food (e.g., epiphytic algae) in the presence of seagrass vegetation.

Environmental and spatial controls of macroinvertebrate functional assemblages in seagrass ecosystems along the Pacific coast of northern Japan

“…From the perspective of macroinvertebrate functional diversity, the different patterns of metacommunity structure among functional groups shown in this study could be explained by the variation in ecosystem functions performed by the faunal community in different seagrass patches. For example, the small contribution of environmental controls in determining community structure in the DF and BF groups, but their strong association with seagrass patches (as reported by Barberá-Cebrián et al, 2002;Yamada et al, 2007b;Yamada and Kumagai, 2012), implies that the existence of patchy seagrass alone -without consideration of the vegetation traits -determines the community structure of the DF and BF groups. If so, the existence of more or less patchy seagrass should elicit the assembly of the DF and BF groups and thus ensure the ecological functions provided by these functional groups.…”

“…Boström et al, 2006;Yamada et al, 2007a). For example, it suggested that habitat selections are similar among mysid species in seagrass meadow (Yamada and Kumagai, 2012). Namely, many mysid species occur (i.e., increase their biomass) at same sites with same periods (e.g.…”

“…In contrast, mobile macroinvertebrate species rarely attach themselves to seagrass blades or benthic substrates and instead continuously drift in the water column (e.g. Yamada and Kumagai, 2012). Therefore, such species were classified as the drift-faunal (DF) functional group.…”