Relationships between spatial patterns of benthic assemblages in a mangrove forest using different levels of taxonomic resolution

Abstract

ABSTRACT-The use of multivariate techniques to quantify spatlal and temporal patterns in assemblages requires decisions about the resolution to wlhich taxa are identified Sim~lar spatial patterns in assemblages are often found whether coarse or fine levels of taxonomic resolution are used. Whether coarser resolution retains patterns of relative difference In assemblages between habitats at a hicrarchy of spatial scales has not been widely examined. Where organisms are patchy at many spatial scales, numerous replicates are needed to represent assemblages adequately Identifying taxa into broad groups is generally quicker and cheaper than identification to species, so coarser resolution may release limited resources for the intensive sampling necebsdry for populations of highly dispersed and patchy organisms. In this study, intertidal epifaunal assemblages in urban mangrove forests were examined at scales of metres, tens of metres and hundreds of metres using 2 different levels of taxonomic resolution 93 taxa and 9 broad groups. Bray-Curtis measures of dissimilarity were also compared between the 2 levels of taxonomic resolution to test the hypothesis that quantitative differences in the assemblages at a hierarchy of spatial scales were retained with different levels of taxonomic resolution. Assemblages varied at each spatial scale. Similar patterns were obtained at each level of taxonomic resolution because the Bray-Curtis measures of dissimilarity were strongly correlated between the 2 1evc:ls. More variable sites, as identified using one level of taxonomic resolution, were also more variable using a different level of taxonomic resolution. Also, sites that were similar to each other when 93 taxa were used remained similar when the taxa were grouped into 9 groups. Transforming the data to the fourth root retained patterns of differences between sites, but altered patterns of variability within sites. The relative value of putting limited resources into increasing the size of the sample as opposed to increased taxonomic resolution in such habitats is discussed.

Effects of urban wastewater on crab and mollusc assemblages in equatorial and subtropical mangroves of East Africa

“…Indeed, a strong variability was also evident at the local scale, with the two non-urban forests in each country differing significantly from each other. However, this source of variability was anticipated from previous studies on mangrove macrobenthic infauna (Chapman, 1998;Kelaher et al, 1998;Chapman and Tolhurst, 2004) and other more general studies on spatial patterns of benthos in intertidal habitats (Thrush et al, 1994;Underwood and Chapman, 1998).…”

Influence of taxonomic resolution, biological attributes and data transformations on multivariate comparisons of rocky macrofaunal assemblages

“…The ability of higher taxa to discriminate between assemblages has been attributed to functional coherence among species within higher taxa (Warwick 1993), redundancy of information in species-level data sets (Gray et al 1988, Chapman 1998) and a hierarchical structure in biological response to stress (Ferraro & Cole 1990). The latter theory assumes that as stress increases, the adaptability of species is exceeded, in turn, by that of genera, families, orders, classes and phyla.…”

Effectiveness of different investigation procedures in detecting anthropogenic impacts on coralligenous assemblages

“…Identifying suitable assemblage descriptors that are sensitive to human-induced stress is very important in impact evaluation studies, because it optimizes sampling efforts and allows representative patterns of assemblage variability to be obtained (Chapman 1998). According to the objectives of the study, the grouping of species sharing the same general taxonomic or morphological traits may be advantageous for many reasons.…”