Areas Of High Species Richness Research Articles

Using ecological niche modelling to identify diversity hotspots for the herpetofauna of Pacific lowlands and adjacent interior valleys of Mexico

This article documents the conservation status of the herpetofauna in the Pacific lowlands and adjacent Balsas Basin and Chiapas Depression regions and the presents the results of modelling species spatial distributional patterns through GARP analysis, to identify hotspots of species richness, endemic and geographically restricted species in the study area. It also compares the distribution of these hotspots with the distribution of protected areas and intact seasonally tropical dry tropical forests, the dominant vegetation type in the study area and experiencing high deforestation rates. A total of 301 reptiles and amphibian species occur in the study area accounting for a third of the Mexican herpetofauna, and recording high levels of endemism and endangerment. Hotspots of species richness and endemism were located in coastal Jalisco, a considerable portion of the Colima state, as well as scattered areas in Michoacán, Guerrero, and Oaxaca. These areas should receive highest priority for protection. Unfortunately, there was a minimum correspondence when comparing the distribution of actually and proposed protected areas with hotspots identified. Fortunately, areas of high species richness, endemism and restricted species coincided with those where intact seasonally tropical dry tropical forests still exists. These areas should receive high priority in future plans for seasonally tropical dry tropical forests protected areas. It is hoped that this paper will call attention to the need for establishing a network of protected areas in the study area, as has been proposed by previous studies.

Species richness and biodiversity conservation priorities in British Columbia, Canada

Patterns in the geographic distribution of seven species groups were used to identify important areas for conservation in British Columbia, Canada. Potential priority sites for conservation were determined using an integer programming algorithm that maximized the number of species represented in the minimum number of sites. Sweep analyses were used to determine how well the set of priority sites identified for each species group represented the other species groups. Although areas of highest species richness were different for each species group, they all included sites in the southern interior of British Columbia, where there is limited protection. Furthermore, less than 13% of the distribution ranges for 23 of 25 bird species of special conservation concern were located within existing protected areas. Species at risk of extinction were poorly represented (26%–42%) in priority sets of sites selected for amphibians, reptiles, birds, and mammals, since these sites were generally scattered throughout the province. However, priority sites for species at risk represented 72%–91% of the species in other groups. Therefore, conservation activities in sites identified for such species have the potential to benefit many other species. These sites could be investigated in more detail to augment existing conservation and protection efforts in British Columbia.

Phytogeography, range size and richness of Australian endemic Sauropus (Euphorbiaceae)

AbstractAim To investigate the distribution of Australian species of Sauropus. The information obtained is used to (1) identify areas of highest richness and centres of endemism, (2) investigate latitudinal gradients of richness and range size, (3) determine the types of rarity shown, and (4) provide hypotheses on historical biogeography of the genus within Australia.Location Australia.Methods Specimens from 17 herbaria and field searches were examined and label and field information collated on distribution, habit and habitat. Distribution information was used to map all species within 784 grid cells of 1° × 1° and within the 97 Australian ‘ecological regions’. Morphometric cluster analysis of species was conducted using Kulczynski association and flexible UPGMA on 23 character states. Simple regression was used to correlate species richness, density and range size to changes in latitude. CLIMEX is used to match the climate of the region of highest richness in Australia with other areas of the world.Results Species richness was highest within the tropical north of Australia, and most species were associated with tropical savanna woodlands. Two areas were identified as centres of endemism and these corresponded closely to areas of high species richness. Four morphological groups were identified. One species (Sauropus trachyspermus) was found to be widespread, however all other species had small geographical ranges. Species richness and range size were significantly correlated with changes in latitude. Ten species were found to be of the rarest type, warranting conservation initiatives.Main conclusions Two regions of high richness and endemism of Sauropus occur, Thailand and Australia. Within Australia, the Kakadu‐Alligator River and the Cairns‐Townsville areas were identified as centres of endemism and high species richness for Sauropus. Australian Sauropus in general occur in similar communities and climates as other members of the genus elsewhere. Ten of the 27 species of Australian endemic Sauropus are extremely rare and warrant conservation initiatives. Correlations of latitude to species richness are potentially due to Sauropus radiating from the climatically stable top end of Australia. Increasing range size in more southern latitudes may also be due to stability of climates in the top end or because there is more available land area at these latitudes. Sauropus micranthus, the only non‐endemic species, is probably a more recent invader from the Tertiary period when tropical rain forests where more extensive and congruent with those of New Guinea.

Changes in forest vegetation and arbuscular mycorrhizae along a steep elevation gradient in Arizona

We assessed species composition, richness and abundance of understory vegetation, as well as arbuscular mycorrhizal (AM) inoculum potential on the San Francisco Peaks, tallest mountains in Arizona, crossing a steep, south-facing elevational gradient. These mountains have a high conservation value due to their rare habitats but previous vegetation studies have been limited. Because mature trees in the Pinaceae do not form associations with AM fungi, there may be more variation in plant community and AM fungal associations in coniferous forest than in ecosystems where all species associate with AM fungi. Differences in species composition between forest types reflected differences in the historical disturbance regimes. Species richness was highest in ponderosa pine forest (32.6 ± 1.4 per 1000 m 2 plot), although plant abundance was highest in aspen forest (49.4 ± 3.8%). Ponderosa pine and bristlecone pine forest were both high in species richness and contained species which were tolerant of frequent, low-intensity fire. Exotic species richness and abundance were highest in the lower elevations, which were also areas of high species richness and greater anthropogenic disturbance. Arbuscular mycorrhizal inoculum potential varied widely (1.2–80.1%), decreasing with increases in tree cover. We suggest indicator species that may be of use in monitoring these forests under changing climate and fire regimes.

Primary productivity and species richness: relationships among functional guilds, residency groups and vagility classes at multiple spatial scales

One of the major determinants of species richness is the amount of energy available, often measured as primary productivity. Heterogeneity of environmental variables has also been found to influence species richness. Predicting species distributions across landscapes and identifying areas that have high species richness, or vulnerable groups of species, is useful for land management. Remotely sensed data may help identify such areas, with the Normalized Difference Vegetation Index (NDVI) providing an estimate of primary productivity. We examined the relationship between maximum productivity (NDVI), heterogeneity of productivity, and species richness of birds and butterflies at multiple spatial scales. We also explored relationships between productivity, functional guilds and residency groups of birds, and vagility classes of butterflies. Positive linear relationships between maximum NDVI and number of functional guilds of birds were found at two spatial scales. We also found positive linear relationships between maximum NDVI and species richness of neotropical migrant birds at two scales. Heterogeneity of NDVI, by contrast, was negatively associated with number of functional guilds of birds and species richness of resident birds. Maximum NDVI was associated with species richness of all butterflies and of the most vagile butterflies. No association was found between heterogeneity of NDVI and species richness of butterflies. In the Great Basin, where high greenness and availability of water correspond to areas of high species richness and maximum NDVI, our results suggest that NDVI can provide a reliable basis for stratifying surveys of biodiversity, by highlighting areas of potentially high biodiversity across large areas. Measures of heterogeneity of NDVI appear to be less useful in explaining species richness.

Regional land-use impacts affecting avian richness patterns in Southern Africa-insights from historical avian atlas data

Biodiversity conservation is a challenge within developing regions of the world. Landscape heterogeneity is largely directed by interconnected economic and social systems, which are largely driven by political, communal, and private control of the land estate. There is increasing evidence that areas of high species richness may coincide with dense human settlement. Influences of landscape pattern, human impact, and divergent past political land management on functional groups of bird species richness were examined in KwaZulu–Natal, South Africa. The functional groups included species of breeding, non-breeding, generalist, and specialist birds. A database of land-use/land-cover (LULCC) and human impact indicators was used to develop relationships and infer historic changes in bird richness derived from two censusing periods (1975–1979 and 1988–1992). The objective was to examine richness and compare relationships based on analyses using land management regions, avifaunal zones and socio-economic regions. Paired and two-sample t-tests documented differences in richness among land management regions and between regions over time. Landscape metrics, LULCC proportion, and other human impact variables were examined using Monte Carlo permuted multiple regressions to develop relationships for bird richness groups. Significant increases in bird group richness were shown between survey periods, as well as differences between land management regions. The statistical models explained 22–79% of variation in bird richness among avifaunal zones by functional group, and 32–99% of variation in bird richness among the socio-economic regions. The majority of the relationships were explained by LULCC proportion rather than landscape metrics denoting spatial arrangement. The analysis concludes that there have been significant increases in bird richness apparently related to land-use development during the study period. The apparent increase in richness may be due to maintenance of original vegetation-specific species in untransformed fragments in highly transformed areas combined with species that exploit transformed habitats well in the transformed areas. It is concluded that research on the interface between biogeography and human development should be seen as a perquisite for conservation assessments in developing regions of the world.

Biogeographic Crossroads as Priority Areas for Biodiversity Conservation

Abstract: Threats to biodiversity outpace the resources of the conservation community and necessitate careful prioritization of conservation actions. I suggest that targeting the regions where biogeographic assemblages intersect—“biogeographic crossroads”—is a strategy that may achieve significant conservation economy by focusing on areas that satisfy many conservation criteria. I used a combination of data on Scarabaeine beetles in Bolivia and on other taxa and locations from the literature to consider the short‐ and long‐term benefits of conserving these biogeographic crossroads. Biogeographic crossroads are areas of high species richness and beta diversity, often across many taxonomic groups. They are also regions where representativeness can be achieved with relative efficiency. Recent evidence that ecotones may be loci of evolution suggests that evolutionary processes such as speciation and coevolution may be conserved at biogeographic crossroads. Biogeographic crossroads appear to be areas of high conservation priority and opportunity in both the short and long term and require increased attention in the process of setting conservation priorities.

Avian Studies in Montane Meadows: Songbird Abundance and Nesting Success

The loss of biological diversity has become a global concern during the last decade (Wilson, 1988; Reid and Miller, 1989). The need to predict those species of concern and areas of high species richness is even more pressing as we enter an era of potential global climate change. Prerequisites to good decision-making with regard to the management of biological diversity are adequate floral and faunal inventories for the lands in question and a rigorous understanding of species-habitat relationships (e.g., Noss, 1983; Davis et al., 1990; Scott et al., 1990; Scott et al., 1993). The emergence of landscape ecology as a discipline has been instrumental in helping scientists understand spatial patterns of species distribution (Noss, 1983; Urban et al., 1987; Turner, 1989). Once these relationships are understood, it may be possible to predict species diversity based upon landscape level habitat analysis using geographic information systems (GIS) and remotely sensed data (Urban et al., 1987; Turner, 1989) at fine-scale resolutions (e.g., 20 - 50 meter sampling sites). Conversely, such analyses can help optimize sampling strategies or allow us to test hypotheses regarding the spatial correspondence of species diversity "hotspots" among taxonomic groups (e.g. Prendergast et al., 1993). The debate over global climate change has created renewed interest in documenting baseline variability in biodiversity. Goals of the Committee on Earth Sciences (1989) regarding the U.S. Global Change Research Program focus on the development of sound scientific strategies for monitoring and predicting environmental change. Key priorities, as noted by the committee, are as follows: "Systematic sampling and monitoring are essential to document critical natural versus human-induced change in the structure and function of globally relevant biological systems on various time scales." (Committee on Earth Sciences, 1989).

Patterns of mammalian species richness and habitat associations in Pennsylvania

Landscape variables were employed as indices of habitat heterogeneity, fragmentation, and human influence on the environment to characterize constituent units of a 635 km 2 grid covering the state of Pennsylvania. Species richness was determined by overlaying the distributions of all 60 terrestrial mammalian species found within the state. All landscape variables investigated were correlated with species richness. Areas with high topographic variation and low road density had the highest species richness. Species sensitive to habitat fragmentation were also associated with large forest patches and low road density. These landscape variables may be useful in identifying areas that are important for the conservation of these species. Associations between species distributions and landscape variables were substantiated by published habitat associations. Species with extremely limited distributions were not associated with landscape variables and represent special cases for conservation planners. Rare species, as defined by their limited geographical distribution, were not associated with areas of high species richness (hotspots). The utility of species richness hotspots for conservation planning is disputable. Hotspots of species richness were associated with large forest patches and low road density.

The biogeography of the Anura of sub-equatorial Africa and the prioritisation of areas for their conservation

There is an increasing need for protected areas to conserve biodiversity efficiently. The Anura of sub-equatorial Africa have received little attention, but we quantitatively analyse a database containing presence-only data for anurans of sub-equatorial Africa to determine patterns of distribution and species richness, and discuss the roles of present and past environmental conditions in shaping these patterns. We consider the distribution of areas rich in endemic, range-restricted and Red Data Book (RDB) species to identify areas of significance to conservation. The Eastern Highlands of Zimbabwe and adjacent area in Mozambique, southeastern Malawi and the northern coast of KwaZulu/Natal are particularly species rich, whereas the southwestern Cape of South Africa and northwestern Zambia exhibit high degrees of endemism. Four major biogeographical sub-regions are identified, which can be further subdivided into provinces. All statistically significant, current environmental factors together account for 52.6% of species richness. Annual maximum rainfall, soil type variation, minimum temperature and range of elevation were all positively correlated with species richness. Thus, both habitat influences and history appear to have influenced patterns of anuran richness in the region. Generally, areas of high species richness coincide with those high in range-restricted, endemic and RDB species. In South Africa, the northeastern coast and southwestern Cape are hypothesised to have been both refugia and centres of speciation. Results suggest that the current reserve system in sub-equatorial Africa is inadequate for the conservation of the full complement of anuran species in the region.

A preliminary assessment of the contribution of nature reserves to biodiversity conservation in Great Britain

AbstractAs a signatory of the Convention on Biological Diversity, the United Kingdom (UK) Government is obliged to conserve and enhance biodiversity. One step towards addressing this goal is to determine the level of biodiversity conservation already achieved within the current array of protected areas. We used national distribution data for ten taxonomic groups, and location information for three reserve networks, to assess the contribution of nature reserves to biodiversity conservation in Great Britain at the 10 km square (=100 km2) resolution. For several taxonomic groups, 10 km squares containing nature reserves had a significantly greater overlap than random networks with both hotspots (areas of high species richness) and complementary areas (sets of sites within which all species are represented). In addition, more than 94% of species from each taxonomic group have been recorded within the 10 km squares of the three reserve networks. These results provide some encouragement in terms of the UK meeting its commitment to conserve biodiversity.

National-scale conservation assessments at an appropriate resolution

Abstract. Most national-scale conservation assessments are carried out at a resolution that is different from the actual size of protected areas in the study region. Coincidence between nature reserves and both hotspots (areas of high species richness) and complementary areas (sets of sites within which all species are represented) have been reported. However, the resolution (size of grid cells) of the species’ distribution data upon which many of these studies are based is often close to an order of magnitude larger than the size of the reserves. Presumably, only a proportion of the species recorded in the coarse grid cells will actually be present on reserves. We use fine (2 × 2-km square grid cells) and coarse (10 × 10-km square grid cells) resolution data of national distributions for breeding birds throughout Great Britain, and presence data for avian species on Royal Society for the Protection of Birds (RSPB) nature reserves, to investigate the proportion of species in the local area (100 km2) that are actually present on reserves. RSPB reserves contain between 50% and 70% of species from the local area. These proportions are significantly higher than for randomly selected, non-reserve areas, indicating that RSPB reserves contain higher concentrations of bird species than the wider countryside. Furthermore, on RSPB reserves these proportions of threatened and non-threatened species are equal, whereas in non-reserve areas the proportions of non-threatened species are significantly higher than threatened species. Thus, reserves hold a higher proportion of threatened species than occurs in the wider countryside.

Birds as biodiversity indicators in the planning of Forest Nature Reserves in Uganda

Baltzer, M., Matthews, R., Howard, P., Kigenyi F. & Viskanic, P. 2000. Birds as biodiversity indicators in the planning of Forest Nature Reserves in Uganda. Ostrich 71 (1 & 2): 291. In Uganda a policy decision has been taken to set aside 20% of the nation's 1.4 million hectare forest estate as Forest Nature Reserves, for the protection of biodiversity. The estate comprises 713 Forest Reserves, ranging in size from just a few hectares to well over 100 000 hectares, scattered all over the country. In order to select appropriate areas for designation as Nature Reserves, the Forest Department (with assistance from the European Community and Global Environmental Facility) has evaluated all the larger reserves for biodiversity, focusing on birds and four other biological indicator groups (woody plants, mammals, butterflies and moths). Building on earlier work, teams of departmental staff carried out detailed systematic biodiversity surveys of 65 major forests between May 1992 and March 1995. The work on birds involved 1 442 person-days of field observation and 1.2 million metre net-hours of mist-netting effort. Altogether 5 744 species-site records were made, involving 604 of Uganda's 1011 species: this brings the total number of species known from Uganda's forest reserves to 841 (83% of the country's birds). Several species not previously known from Uganda were recorded, especially in the north and east of the country where birds of the northern (Sudan/Guinea) savannas and Somali-Masai regions reach the extreme limits of their ranges. The bird data have been analysed alongside comparable data for the other four indicator taxa. Fortunately, areas of high species richness and levels of endemism for the five groups tend to coincide. Priority conservation sites have been identified and a national network of Forest Nature Reserves has been designed as part of a representative and efficient protected areas system for Uganda.

EXOTIC PLANT SPECIES INVADE HOT SPOTS OF NATIVE PLANT DIVERSITY

Some theories and experimental studies suggest that areas of low plant species richness may be invaded more easily than areas of high plant species richness. We gathered nested-scale vegetation data on plant species richness, foliar cover, and frequency from 200 1-m2 subplots (20 1000-m2 modified-Whittaker plots) in the Colorado Rockies (USA), and 160 1-m2 subplots (16 1000-m2 plots) in the Central Grasslands in Colorado, Wyoming, South Dakota, and Minnesota (USA) to test the generality of this paradigm. At the 1-m2 scale, the paradigm was supported in four prairie types in the Central Grasslands, where exotic species richness declined with increasing plant species richness and cover. At the 1-m2 scale, five forest and meadow vegetation types in the Colorado Rockies contradicted the paradigm; exotic species richness increased with native-plant species richness and foliar cover. At the 1000-m2 plot scale (among vegetation types), 83% of the variance in exotic species richness in the Central Grasslands was explained by the total percentage of nitrogen in the soil and the cover of native plant species. In the Colorado Rockies, 69% of the variance in exotic species richness in 1000-m2 plots was explained by the number of native plant species and the total percentage of soil carbon. At landscape and biome scales, exotic species primarily invaded areas of high species richness in the four Central Grasslands sites and in the five Colorado Rockies vegetation types. For the nine vegetation types in both biomes, exotic species cover was positively correlated with mean foliar cover, mean soil percentage N, and the total number of exotic species. These patterns of invasibility depend on spatial scale, biome and vegetation type, spatial autocorrelation effects, availability of resources, and species-specific responses to grazing and other disturbances. We conclude that: (1) sites high in herbaceous foliar cover and soil fertility, and hot spots of plant diversity (and biodiversity), are invasible in many landscapes; and (2) this pattern may be more closely related to the degree resources are available in native plant communities, independent of species richness. Exotic plant invasions in rare habitats and distinctive plant communities pose a significant challenge to land managers and conservation biologists.

Exotic Plant Species Invade Hot Spots of Native Plant Diversity

Some theories and experimental studies suggest that areas of low plant species richness may be invaded more easily than areas of high plant species richness. We gathered nested-scale vegetation data on plant species richness, foliar cover, and frequency from 200 1-m2 subplots (20 1000-m2 modified-Whittaker plots) in the Colorado Rockies (USA), and 160 1-m2 subplots (16 1000-m2 plots) in the Central Grasslands in Colorado, Wyoming, South Dakota, and Minnesota (USA) to test the generality of this paradigm. At the 1-m2 scale, the paradigm was supported in four prairie types in the Central Grasslands, where exotic species richness declined with increasing plant species richness and cover. At the 1-m2 scale, five forest and meadow vegetation types in the Colorado Rockies contradicted the paradigm; exotic species richness increased with native-plant species richness and foliar cover. At the 1000-m2 plot scale (among vegetation types), 83% of the variance in exotic species richness in the Central Grasslands was explained by the total percentage of nitrogen in the soil and the cover of native plant species. In the Colorado Rockies, 69% of the variance in exotic species richness in 1000-m2 plots was explained by the number of native plant species and the total percentage of soil carbon. At landscape and biome scales, exotic species primarily invaded areas of high species richness in the four Central Grasslands sites and in the five Colorado Rockies vegetation types. For the nine vegetation types in both biomes, exotic species cover was positively correlated with mean foliar cover, mean soil percentage N, and the total number of exotic species. These patterns of invasibility depend on spatial scale, biome and vegetation type, spatial autocorrelation effects, availability of resources, and species-specific responses to grazing and other disturbances. We conclude that: (1) sites high in herbaceous foliar cover and soil fertility, and hot spots of plant diversity (and biodiversity), are invasible in many landscapes; and (2) this pattern may be more closely related to the degree resources are available in native plant communities, independent of species richness. Exotic plant invasions in rare habitats and distinctive plant communities pose a significant challenge to land managers and conservation biologists.

ASSESSING CONSERVATION PRIORITIES IN MEGADIVERSE MEXICO: MAMMALIAN DIVERSITY, ENDEMICITY, AND ENDANGERMENT

The identification of areas of high priority for conservation is becoming a major endeavor for conservation biologists. Regions of high species richness and high concentrations of endemic and endangered species have been considered a priority for conservation. In this paper we use information about the species richness, composition, and distribution of mammals from Mexico for selecting priority areas for conservation. All species of terrestrial mammals were characterized by geographic range size, body mass, and conservation status, and their distributions were overlaid on a 2° × 2° grid to detect areas of high concentrations of species richness, endemicity, and endangered species. We focused our analyses at both species and biogeographic levels. At the species level we examined differences among endangered, endemic, and non-endemic species in ecological characteristics correlated with vulnerability to extinction. There were significant differences between endangered and non-endangered species, and between endemic and non-endemic mammals in body size and geographic range size. At the biogeographic level simple correlation analyses were carried out to determine the relation between latitude, total species richness, number of endemic species, and number of endangered species. We found a very low correspondence among areas of high diversity, high endemicity, or high number of endangered species. The distribution of many species with restricted geographic ranges, including endemic and non-endemic species, did not coincide with areas of high species richness, endemicity, or endangerment. We suggest a conservation strategy that gives priority to areas of high concentration of endangered species and of non-endangered species with restricted distributions. Among endangered species a higher priority should be given to endemic taxa vs. non-endemic species, and to restricted species over widespread taxa in these two groups.

Use Of Databases For Research and Conservation of the Eastern Arc Mountains

The establishment and use of computer databases to hold biological records is common in many countries. Such systems can accommodate a large volume of data with many potential uses, but many databases have failed due to poor design or programming, or to the lack of a proper user-need analysis. In all biological databases there are problems with the data being used. The most common problems are uneven collection effort, taxonomic confusion leading to unreliable records, difficulties with finding exact collection localities, differences in map projections leading to inaccurate record positions and more.Data in databases, either the raw biological records, or interpreted/modelled range distributions, can be used for analyses of value to both conservationists and to academic biogeographers. However, all such analyses are highly influenced by the analytical scale, and results from one scale cannot be used at another. This is a fundamental problem with analyses using computerised data, especially for conservation planning. Data at different scales can be used to illustrate areas of high species richness, or areas where species of narrow distributional range congregate, although the results from one scale may not be applicable at another.Computer programs can be used to select areas so that all species in the database are covered. The last method, using the principles of complementarity, is the most efficient way to select ‘ideal’ conservation areas. With such an analysis the theoretical minimum number of areas required to conserve all the species within a given database (e.g. all the birds in Sub-Saharan Africa) can be chosen. However, all such analyses are only indicative, as they do not take into consideration population viability, threats to the areas selected, or other ‘real-world’ variables that are important when conservation plans are being formulated.For academics the patterns of species richness and range-restriction (i.e. endemism) can be used in large-scale models that can develop and test hypotheses to explain why species are distributed as they are and how evolution/extinction may have operated over time in order to produce the patterns observed. Such studies can have relevance to the development of conservation plans at the broad scale.

Demersal fish community diversity off New Zealand: Is it related to depth, latitude and regional surface phytoplankton?

Recent studies of basin-scale patterns of diversity of benthic macrofauna reported strong latitudinal gradients of diversity in the deep North Atlantic, in contrast to regionally variable patterns in the Southern Hemisphere. Here we use data from fisheries research trawl surveys to examine spatial patterns of species richness, Shannon-Wiener diversity index, and evenness of demersal fish communities in relation to latitude and depth from 80 to 898 m off south-east New Zealand. We found species richness decreased latitudinally within regions in the poleward direction, and increased with depth. Areas of high species richness were concentrated along the margins of the Chatham Rise and were associated with current intensification in regions of enhanced surface phytoplankton pigment concentration. Species richness was highest between the 500 and 1000 m contours on the Chatham Rise, where enhanced surface phytoplankton pigment is associated with a major oceanographic feature, the Subtropical convergence. A predominance of species-rich locations was found on the more steeply shelving northern margin of the Chatham Rise. The regional latitudinal pattern of diversity appears to be correlated with regional production, and to be influenced by mesoscale oceanographic features constrained by the bathymetry, although the proximal causes for high diversity remain speculative.