Species richness

About: Species richness is a research topic. Over the lifetime, 61672 publications have been published within this topic receiving 2183796 citations.

Recent advances in the study of long-distance dispersal of aquatic invertebrates via birds

Abstract: Although Darwin pioneered the study of long-distance dispersal (LDD) of aquatic invertebrates via waterbirds, it remains in its infancy as a modern discipline. A handful of recent studies have quantified internal or external transport in the field, confirming that a variety of long-distance migrants carry invertebrates both internally and externally. These studies show that variation in the morphology of vectors influences the frequency and size of propagules transported, and suggest that more invertebrate groups disperse via birds than was previously thought. Dispersal limitation has mainly been investigated for zooplankton in small experimental systems from which waterbirds were effectively excluded, and the extent of such limitation for invertebrate populations in wetlands interconnected by waterbird movements remains unclear. We expect that the spatial and temporal scales at which dispersal limitation constrains geographical ranges, species richness and genetic structure of invertebrates depends partly on the density of migratory birds using the area. Birds may have a major role in the expansion of exotic species. We propose several avenues for future research. There is a particular need for more quantitative studies of LDD by birds that will enable modellers to assess its role in maintaining invertebrate biodiversity among increasingly fragmented wetlands and in the face of climate change, as well as in the spread of invasive species.

A synthesis of plant invasion effects on biodiversity across spatial scales

Abstract:  Premise of the study: Invasive plant species are typically thought to pose a large threat to native biodiversity, and local-scale studies typically confi rm this view. However, plant invaders rarely cause regional extirpations or global extinctions, causing some to suggest that invasive species ’ infl uence on native biodiversity may not be so dire. We aim to synthesize the seemingly confl icting literature in plant invasion biology by evaluating the effects of invasive plant species across spatial scales.  Methods: We fi rst conducted a meta-analysis on the effects of invasive plants on the species richness of invaded communities across a range of spatial extents. We then discuss studies that consider the role of invasive plants on regional spatial scales for which such meta-analyses are not possible. Finally, we develop a conceptual framework to synthesize the infl uence of invasive species across spatial scales by explicitly recognizing how invasive species alter species-occupancy distributions.  Key results: We found a negative relationship between the spatial extent of the study and the effect size of invasive plants on species richness. Our simulation models suggest that this result can occur if invaders, either proportionately or disproportionately, reduce the occupancy of common species to a greater degree than rare species.  Conclusions: Future studies should consider the infl uence of invaders on the abundance and occupancy-level changes in native species to inform how invasive plants will infl uence native species richness relationships across spatial scales. This approach will allow greater predictive ability for forecasting changes in biodiversity in the face of anthropogenic biological invasions and will inform invasive species management and restoration.

Floristic diversity and structure of upland and arroyo forests of coastal Jalisco.

Abstract: The species richness at Chamela, Jalisco (average annual rainfall 748 mm, with a 4-month wet season), exceeded that of other Neotropical dry forests with more than twice its annual rainfall. Transect samples totaling 0.3 ha included 176 species and 1352 plants -2.5 cm DBH. The mean number of species per 100-m2 transect was 22.7. Upland and arroyo sites were similar in species number, but the latter included greater percentages of species of vines (11% vs 21%) and trees 10 cm DBH (24% vs 31%). The only species that were both common and ubiquitous were Trichilia trifolia, Caesalpinia eriostachys, and Cordia alliodora. Upland sites were typified by species of Croton, Lonchocarpus, and Cordia, and arroyo sites were typified by Thouinidium decandrum and a variety of vines. Families with the most species were Leguminosae, Euphorbiaceae, Rubiaceae, and Bignoniaceae. Total basal area averaged 0.24 m2/100 m2 in uplands but 0.52 m2/100 m2 in arroyos; most of the difference was due to trees -30 cm DBH. In all sites, over 50 percent of the stems were < 5 cm DBH, but vines and large trees were more abundant in arroyos. Stem densities averaged about 45/100 m2 in both sites.

Consistent patterns and the idiosyncratic effects of biodiversity in marine ecosystems.

Abstract: Revealing the consequences of species extinctions for ecosystem function has been a chief research goal and has been accompanied by enthusiastic debate. Studies carried out predominantly in terrestrial grassland and soil ecosystems have demonstrated that as the number of species in assembled communities increases, so too do certain ecosystem processes, such as productivity, whereas others such as decomposition can remain unaffected. Diversity can influence aspects of ecosystem function, but questions remain as to how generic the patterns observed are, and whether they are the product of diversity, as such, or of the functional roles and traits that characterize species in ecological systems. Here we demonstrate variable diversity effects for species representative of marine coastal systems at both global and regional scales. We provide evidence for an increase in complementary resource use as diversity increases and show strong evidence for diversity effects in naturally assembled communities at a regional scale. The variability among individual species responses is consistent with a positive but idiosyncratic pattern of ecosystem function with increased diversity.