Species richness

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

How Many Species of Insects and Other Terrestrial Arthropods Are There on Earth

Abstract: In the last decade, new methods of estimating global species richness have been developed and existing ones improved through the use of more appropriate statistical tools and new data. Taking the mean of most of these new estimates indicates that globally there are approximately 1.5 million, 5.5 million, and 7 million species of beetles, insects, and terrestrial arthropods, respectively. Previous estimates of 30 million species or more based on the host specificity of insects to plants now seem extremely unlikely. With 1 million insect species named, this suggests that 80% remain to be discovered and that a greater focus should be placed on less-studied taxa such as many families of Coleoptera, Diptera, and Hymenoptera and on poorly sampled parts of the world. DNA tools have revealed many new species in taxonomically intractable groups, but unbiased studies of previously well-researched insect faunas indicate that 1–2% of species may be truly cryptic.

An evaluation of camera traps for inventorying large‐ and medium‐sized terrestrial rainforest mammals

Abstract: Mammal inventories in tropical forests are often difficult to carry out, and many elusive species are missed or only reported from interviews with local people. Camera traps offer a new tool for conducting inventories of large- and medium-sized terrestrial mammals. We evaluated the efficiency of camera traps based on data from two surveys carried out at a single site during 2 consecutive years. The survey efforts were 1440 and 2340 camera days, and 75 and 86% of the 28 large- and medium-sized terrestrial mammal species known to occur at the site were recorded. Capture frequencies for different species were highly correlated between the surveys, and the capture probability for animals that passed in front of the cameras decreased with decreasing size of the species. Camera spacing and total survey area had little influence on the number of species recorded, with survey effort being the main factor determining the number of recorded species. Using a model we demonstrated the exponential increase in survey effort required to record the most elusive species. We evaluated the performance of different species richness estimators on this dataset and found the Jackknife estimators generally to perform best. We give recommendations on how to increase efficiency of camera trap surveys exclusively targeted at species inventories.

Effects of habitat isolation on pollinator communities and seed set

Abstract: Destruction and fragmentation of natural habitats is the major reason for the decreasing biodiversity in the agricultural landscape. Loss of populations may negatively affect biotic interactions and ecosystem stability. Here we tested the hypothesis that habitat fragmentation affects bee populations and thereby disrupts plant-pollinator interactions. We experimentally established small ”habitat islands” of two self-incompatible, annual crucifers on eight calcareous grasslands and in the intensively managed agricultural landscape at increasing distances (up to 1000 m) from these species-rich grasslands to measure effects of isolation on both pollinator guilds and seed set, independently from patch size and density, resource availability and genetic erosion of plant populations. Each habitat island consisted of four pots each with one plant of mustard (Sinapis arvensis) and radish (Raphanus sativus). Increasing isolation of the small habitat islands resulted in both decreased abundance and species richness of flower-visiting bees (Hymenoptera: Apoidea). Mean body size of flower-visiting wild bees was larger on isolated than on nonisolated habitat islands emphasizing the positive correlation of body size and foraging distance. Abundance of flower-visiting honeybees depended on the distance from the nearest apiary. Abundance of other flower visitors such as hover flies did not change with increasing isolation. Number of seeds per fruit and per plant decreased significantly with increasing distance from the nearest grassland for both mustard and radish. Mean seed set per plant was halved at a distance of approximately 1000 m for mustard and at 250 m for radish. In accordance with expectations, seed set per plant was positively correlated with the number of flower-visiting bees. We found no evidence for resource limitation in the case of mustard and only marginal effects for radish. We conclude that habitat connectivity is essential to maintain not only abundant and diverse bee communities, but also plant-pollinator interactions in economically important crops and endangered wild plants.

Invasional 'meltdown' on an oceanic island

Abstract: Islands can serve as model systems for understanding how biological invasions affect community structure and ecosystem function. Here we show invasion by the alien crazy ant Anoplolepis gracilipes causes a rapid, catastrophic shift in the rain forest ecosystem of a tropical oceanic island, affecting at least three trophic levels. In invaded areas, crazy ants extirpate the red land crab, the dominant endemic consumer on the forest floor. In doing so, crazy ants indirectly release seedling recruitment, enhance species richness of seedlings, and slow litter breakdown. In the forest canopy, new associations between this invasive ant and honeydew-secreting scale insects accelerate and diversify impacts. Sustained high densities of foraging ants on canopy trees result in high population densities of hostgeneralist scale insects and growth of sooty moulds, leading to canopy dieback and even deaths of canopy trees. The indirect fallout from the displacement of a native keystone species by an ant invader, itself abetted by introduced/cryptogenic mutualists, produces synergism in impacts to precipitate invasional meltdown in this system.

Spatial modelling of biodiversity at the community level

Abstract: Summary 1Statistical modelling is often used to relate sparse biological survey data to remotely derived environmental predictors, thereby providing a basis for predictively mapping biodiversity across an entire region of interest. The most popular strategy for such modelling has been to model distributions of individual species one at a time. Spatial modelling of biodiversity at the community level may, however, confer significant benefits for applications involving very large numbers of species, particularly if many of these species are recorded infrequently. 2Community-level modelling combines data from multiple species and produces information on spatial pattern in the distribution of biodiversity at a collective community level instead of, or in addition to, the level of individual species. Spatial outputs from community-level modelling include predictive mapping of community types (groups of locations with similar species composition), species groups (groups of species with similar distributions), axes or gradients of compositional variation, levels of compositional dissimilarity between pairs of locations, and various macro-ecological properties (e.g. species richness). 3Three broad modelling strategies can be used to generate these outputs: (i) ‘assemble first, predict later’, in which biological survey data are first classified, ordinated or aggregated to produce community-level entities or attributes that are then modelled in relation to environmental predictors; (ii) ‘predict first, assemble later’, in which individual species are modelled one at a time as a function of environmental variables, to produce a stack of species distribution maps that is then subjected to classification, ordination or aggregation; and (iii) ‘assemble and predict together’, in which all species are modelled simultaneously, within a single integrated modelling process. These strategies each have particular strengths and weaknesses, depending on the intended purpose of modelling and the type, quality and quantity of data involved. 4Synthesis and applications. The potential benefits of modelling large multispecies data sets using community-level, as opposed to species-level, approaches include faster processing, increased power to detect shared patterns of environmental response across rarely recorded species, and enhanced capacity to synthesize complex data into a form more readily interpretable by scientists and decision-makers. Community-level modelling therefore deserves to be considered more often, and more widely, as a potential alternative or supplement to modelling individual species.