Tropical dry forest trees and the relationship between local abundance and geographic range

Aim To test the macroecological principle that a positive relationship exists between local abundance and geographic range size for tree communities in the tropical dry forest. Location Two tropical dry forest (TDF) regions on the Pacific coast of Mexico: one near Chamela, Jalisco; the other near Huatulco, Oaxaca. Methods We recorded species presence and relative abundance of trees and lianas from over 40 locales in each of the study regions using transects across an elevational gradient. We then compared the field data with occurrence data from national and online databases to examine how local patterns of abundance relate to putative geographic range areas and latitudinal breadth. Results We found no significant correlation between abundance and range size. Overall, many more locally abundant species had small ranges than large ones. We found that most species occupy the majority of the TDF range north of Colombia, and those species present in South America occupy the majority of that continent’s TDF range as well. This pattern was independent of local abundance. We also found no relationship between range size and local niche breadth as measured by elevation, or between local abundance and distance to the range centre. Main conclusions The macroecological tenet that posits a positive correlation between local abundance and geographic range size does not appear to hold for TDF trees. The finding that many locally abundant species had narrow ranges also suggests that dry forest endemics may be particularly well adapted to local conditions and make important contributions to community structure. We hypothesize that the absence of abundant species with large ranges is due to opposing environmental constraints that prevent a species from thriving everywhere.     

Neither species geographic range size,climatic envelope,nor intraspecific leaf trait variability capture habitat specialization in a hyperdiverse Amazonian forest

Many plant species exhibit strong association with topographic habitats at local scales. However, the historical biogeographic and physiological drivers of habitat specialization are still poorly understood, and there is a need for relatively easy‐to‐measure predictors of species habitat niche breadth. Here, we explore whether species geographic range, climatic envelope, or intraspecific variability in leaf traits is related to the degree of habitat specialization in a hyperdiverse tropical tree community in Amazonian Ecuador. Contrary to our expectations, we find no effect of the size of species geographic ranges, the diversity of climate a species experiences across its range, or intraspecific variability in leaf traits in predicting topographic habitat association in the ~300 most common tropical tree species in a 25‐ha tropical forest plot. In addition, there was no phylogenetic signal to habitat specialization. We conclude that species geographic range size, climatic niche breadth, and intraspecific variability in leaf traits fail to capture the habitat specialization patterns observed in this highly diverse tropical forest.     

The nutritive values of some major food plants of lechwe, puku and waterbuck along the Chobe River, Botswana

The feeding preferences of lechwe, puku and waterbuck and the nutritive values of the major food plants show a correlation. Within their habitat the species show preference for the plants with the highest crude protein value. The preferred habitats of the species, although overlapping to a certain extent, prevented all three species from using the food plants with the highest protein values at all times. Puku and waterbuck, for example, utilized plants which were clearly inferior to the plant growth available to lechwe in August.     

Drivers and interrelationships among multiple dimensions of rarity for freshwater fishes

Species can be rare or common in three different dimensions: geographic range size, habitat breadth, and local abundance. Understanding drivers of rarity are not only fundamentally interesting; it is also pertinent for their conservation. We addressed this challenge by analyzing the rarity of 291 native freshwater fishes occurring in ca 3500 independent stream reaches that span a broad environmental gradient across continental USA. Using phylogenetic regression and path analysis, we examined the concordance among the three rarity dimensions, and identified possible mechanisms by which species life‐history, habitat affinities, and biogeography drive variation in rarity. Weak double extinction jeopardies were driven by weakly positive correlations between habitat breadth and local abundance, and between habitat breadth and geographic range size. However, a triple extinction jeopardy was averted as local abundance and range size were not positively linked in our study. This is because large‐river and lacustrine habitat use mediated a trade‐off between local abundance and range size. Large rivers and lacustrine habitats represent important dispersal pathways and refugia that enabled fishes to acquire wide ranges; however, species using these habitats are less abundant overall because they are less adapted to small lotic channels, which comprise the majority of stream habitats in the US. Life‐history traits were key in governing the relationship between abundance and range size as large‐river and lacustrine habitat use were driven by body size, egg size, and parental care. Our analysis contributes novel insights into mechanisms that underlie multiple dimensions of rarity in freshwater fish and informs the prioritization of multiply rare species for conservation.     

Evolution of habitat preference in 243 species of Bent‐toed geckos (Genus Cyrtodactylus Gray, 1827) with a discussion of karst habitat conservation

Understanding the processes that underpin adaptive evolutionary shifts within major taxonomic groups has long been a research directive among many evolutionary biologists. Such phenomena are best studied in large monophyletic groups that occupy a broad range of habitats where repeated exposure to novel ecological opportunities has happened independently over time in different lineages. The gekkonid genus Cyrtodactylus is just such a lineage with approximately 300 species that range from South Asia to Melanesia and occupy a vast array of habitats. Ancestral state reconstructions using a stochastic character mapping analysis of nine different habitat preferences were employed across a phylogeny composed of 76% of the known species of Cyrtodactylus. This was done in order to ascertain which habitat preference is the ancestral condition and from that condition, the transition frequency to more derived habitat preferences. The results indicate that a general habitat preference is the ancestral condition for Cyrtodactylus and the frequency of transitioning from a general habitat preference to anything more specialized occurs approximately four times more often than the reverse. Species showing extreme morphological and/or ecological specializations generally do not give rise to species bearing other habitat preferences. The evolution of different habitat preferences is generally restricted to clades that tend to occur in specific geographic regions. The largest radiations in the genus occur in rocky habitats (granite and karst), indicating that the transition from a general habitat preference to a granite or karst‐dwelling life style may be ecologically uncomplicated. Two large, unrelated clades of karst‐associated species are centered in northern Indochina and the largest clade of granite‐associated species occurs on the Thai‐Malay Peninsula. Smaller, independent radiations of clades bearing other habitat preferences occur throughout the tree and across the broad distribution of the genus. With the exception of a general habitat preference, the data show that karst‐associated species far out‐number all others (29.6% vs. 0.4%–10.2%, respectively) and the common reference to karstic regions as “imperiled arcs of biodiversity” is not only misleading but potentially dangerous. Karstic regions are not simply refugia harboring the remnants of local biodiversity but are foci of speciation that continue to generate the most speciose, independent, radiations across the genus. Unfortunately, karstic landscapes are some of the most imperiled and least protected habitats on the planet and these data continue to underscore the urgent need for their conservation.     

Extensive variation,but not local adaptation in an Australian alpine daisy

Alpine plants often occupy diverse habitats within a similar elevation range, but most research on local adaptation in these plants has focused on elevation gradients. In testing for habitat‐related local adaptation, local effects on seed quality and initial plant growth should be considered in designs that encompass multiple populations and habitats. We tested for local adaptation across alpine habitats in a morphologically variable daisy species, Brachyscome decipiens, in the Bogong High Plains in Victoria, Australia. We collected seed from different habitats, controlled for maternal effects through initial seed size estimates, and characterized seedling survival and growth in a field transplant experiment. We found little evidence for local adaptation for survival or plant size, based on three adaptation measures: Home versus Away, Local versus Foreign, and Sympatric versus Allopatric (SA). The SA measure controlled for planting site and population (site‐of‐origin) effects. There were significant differences due to site‐of‐origin and planting site effects. An important confounding factor was the size of plants directly after transplantation of seedlings, which had a large impact on subsequent seedling survival and growth. Initial differences in plant width and height influenced subsequent survival across the growing season but in opposing directions: wide plants had higher survival, but tall plants had lower survival. In an additional controlled garden experiment at Cranbourne Royal Botanic Gardens, site‐of‐origin effects detected in the field experiments disappeared under more benign homogeneous conditions. Although B. decipiens from different source areas varied significantly when grown across a range of alpine habitats, these differences did not translate into a local or habitat‐related fitness advantage. This lack of local advantage may signal weak past selection, and/or weak adaptive transgeneration (plasticity) effects.     

景观基质对雅江中游河谷黑颈鹤冬季觅食地选择的影响

生态系统中生境斑块并非孤立存在,而是嵌于周边景观基质中。生境内种群赖以生存的资源和环境条件不仅取决于生境本身,更与景观基质组成与结构紧密关联。黑颈鹤是青藏高原的旗舰物种,雅鲁藏布江中游河谷高寒湿地是全球最大的黑颈鹤越冬地,为其提供了良好的觅食生境。厘清该区域黑颈鹤觅食生境选择如何受景观基质组成结构的影响,对于青藏高原旗舰物种保护以及流域生态系统综合治理具有重要意义。运用景观生态学原理,以遥感影像和实地黑颈鹤种群调查数据为基础,结合景观基质多尺度缓冲区构建、相关分析以及Maxent模型,分析2000-2020年雅江中游河谷黑颈鹤国家级自然保护区（日喀则片区）景观格局时空变化和觅食地生境特征及其与黑颈鹤种群的关系,探究景观基质对黑颈鹤觅食地选择的影响,并利用关键生境因子模拟黑颈鹤生境适宜性分布。通过分析发现：（1）时间尺度上,雅江中游河谷耕地面积先增加后下降,滩地持续减少;空间尺度上,觅食黑颈鹤种群呈东多西少的集群分布特征,其分布范围与河谷内耕地分布基本吻合;（2）景观基质对黑颈鹤觅食地选择影响显著。景观结构上,黑颈鹤偏好连通性好、优势度高的景观基质;景观组成上,偏好基质中耕地和水域类型,这与黑颈鹤的觅食习性及对环境安全的生态位需求有关;（3）景观基质结构组成对黑颈鹤觅食地选择的影响具有显著的尺度效应。景观基质结构影响最显著的空间尺度为1500-2000m。但基质中耕地、草地和水域等景观组成要素对黑颈鹤的影响具有不同空间尺度效应,分别为1500m、3000m和4000m;（4）通过模型模拟,揭示出黑颈鹤适宜生境面积先增后减,但总体较2000年呈上升趋势,且基质中觅食地与耕地的距离、水域斑块密度和偏好景观组成的优势度始终是生境适宜性解释率最高的景观因子。本研究揭示出,该区域乡村规划应该统筹优化黑颈鹤栖息生境及其景观基质中的作物生产以及居民生活,形成以黑颈鹤旗舰物种保护为核心的高寒湿地生态系统综合管理模式,从而增强青藏高原高寒生态系统的稳定性和可持续性,同时也为深入研究物种生境选择机制提供了思路。     

The effects of host-plant distribution and local abundance on the species richness of agromyzid flies attacking British umbellifers

Abstract. 1. The number of agromyzid species (Diptera: Agromyzidae) attacking British Umbelliferae generally increases with the size of the geographic range of the host, measured as occupied 10 km squares in the Atlas of the British Flora (Lawton & Price, 1979). 2. In the present study we tried to explain the large, residual variation in this species—area relationship using two new variables, namely the local abundance of the host plant, and the number of habitats within which it grows. 3. Local abundance was estimated from eight floras that map plant distributions within English countries by tetrads (2 times 2 km squares). Local abundance was defined as: Total number of occupied tetrads Total number of available tetrads within occupied 10 km squares 4. The number of habitats occupied by each host plant was taken from the only county flora to record plant habitats objectively, that for Warwickshire. 5. We expected to find a correlation between local abundance and the residuals from the national species—area relationship, with locally scarce plants having fewer agromyzids than expected from the sizes of their national ranges, and vice versa. 6. What we found was that size of geographic range and local abundance were highly correlated; hence their relative contributions to agromyzid species richness were difficult to disentangle. Residuals from the national species—area relationship were positively correlated with local abundance, but the relationship marginally failed to achieve statistical significance (P= 0.06). 7. In contrast, the number of habitats occupied by each species of umbellifer in Warwickshire had a marked effect upon agrornyzid species richness, with plants that grow in more habitats supporting more species of insects. Not surprisingly, local abundance and number of habitats occupied were highly correlated. 8. Lawton & Price's observation that aquatic umbellifers are faunally impoverished now emerges as part of the general effect of number of habitats occupied by the host plants on agromyzid species richness. 9. Once the number of habitats occupied by each host plant in Warwickshire was entered into a multiple regression, the effect of size of host geographic range on agromyzid species richness was no longer statistically significant. 10. A combination of the number of habitats occupied, and leaf-form of the host (the latter taken from Lawton & Price, 1979), explains 61% of the variation in agromyzid species richness on British Umbelliferae.     

Fish habitat preferences in large streams of southern France

1. Relationships between fish and their habitat over whole geographic regions, which are evident from studies of many streams and species, can improve understanding of lotic communities and provide reliable management tools. Nevertheless, most habitat preference studies have been based on single sites, and confined to small streams and to game species.
2. Regional habitat preference models, based on local velocity, depth and roughness, were developed for twenty-four species and their size classes commonly found in large European streams. Fish surveys were conducted in six large streams in southern France over an 8-year period. To limit the influences of habitat variables other than those studied, we estimated fish preferences within each survey and averaged this information across surveys. Preferences were fitted with confidence intervals and their sensitivity to field uncertainty was evaluated.
3. Most species and size classes had significant preferences for local habitat conditions which were consistent across the region. Habitat preferences predominant in the region overall were not always observed at any one site, but habitat conditions preferred on average in the region were never actually avoided locally. These results support the use of regional preference models for fish and the development of similar models for other lotic groups whose sensitivity to local habitat conditions has been reported elsewhere.     

Habitat preferences of ptarmigan hunters in Norway

Hunting for willow ptarmigan (Lagopus lagopus) is a popular recreational activity in Norway, but studies of the hunters are limited. While large game management in Norway is based on sound models and research, management of small game hunters and hunting have not been subject to the same rigour. Compared to the extensive body of knowledge about ptarmigan behaviour and habitat preferences, the knowledge base on ptarmigan hunters is very limited. We surveyed the habitat preferences of 3,056 hunters to identify preferred landscape categories using pictures covering a range of landscape types. We also examined to which extent residence types and forms of hunting were related to habitat preferences. Through factor analysis, we identified three categories of hunting habitat; mountain forest, low alpine and high alpine. Mode of hunting is more important than residence status in terms of preferred habitat. Hunters using dogs preferred mountain forest and low alpine habitats more than hunters without dogs. Hunters without dogs had a higher preference than dog hunters for high alpine habitats. Hunters with mixed modes of hunting have wider habitat preferences. Residence status only affects the perception of the mountain forest habitat. The results may have implications for management as land use and place-based meanings are currently changing in many natural and rural landscapes, and hunting needs to be integrated with other recreational uses.     

Topographically controlled thermal‐habitat differentiation buffers alpine plant diversity against climate warming

Aim We aim to: (1) explore thermal habitat preferences in alpine plant species across mosaics of topographically controlled micro‐habitats; (2) test the predictive value of so‐called ‘indicator values’; and (3) quantify the shift in micro‐habitat conditions under the influence of climate warming. Location Alpine vegetation 2200–2800 m a.s.l., Swiss central Alps. Methods High‐resolution infra‐red thermometry and large numbers of small data loggers were used to assess the spatial and temporal variation of plant‐surface and ground temperatures as well as snow‐melt patterns for 889 plots distributed across three alpine slopes of contrasting exposure. These environmental data were then correlated with Landolt indicator values for temperature preferences of different plant species and vegetation units. By simulating a uniform 2 K warming we estimated the changes in abundance of micro‐habitat temperatures within the study area. Results Within the study area we observed a substantial variation between micro‐habitats in seasonal mean soil temperature (ΔT = 7.2 K), surface temperature (ΔT = 10.5 K) and season length (>32 days). Plant species with low indicator values for temperature (plants commonly found in cool habitats) grew in significantly colder micro‐habitats than plants with higher indicator values found on the same slope. A 2 K warming will lead to the loss of the coldest habitats (3% of current area), 75% of the current thermal micro‐habitats will be reduced in abundance (crowding effect) and 22% will become more abundant. Main conclusions Our results demonstrate that the topographically induced mosaics of micro‐climatic conditions in an alpine landscape are associated with local plant species distribution. Semi‐quantitative plant species indicator values based on expert knowledge and aggregated to community means match measured thermal habitat conditions. Metre‐scale thermal contrasts significantly exceed IPCC warming projections for the next 100 years. The data presented here thus indicate a great risk of overestimating alpine habitat losses in isotherm‐based model scenarios. While all but the species depending on the very coldest micro‐habitats will find thermally suitable ‘escape’ habitats within short distances, there will be enhanced competition for those cooler places on a given slope in an alpine climate that is 2 K warmer. Yet, due to their topographic variability, alpine landscapes are likely to be safer places for most species than lowland terrain in a warming world.     

Species number,area and habitat diversity in the Galapagos Islands

The Galapagos vascular plant species are divided into two groups, showing preferences for dry and wet habitats. This division is based on the results of a phytosociological study and is not influenced by such factors as island area, elevation, climate or soil types. The different distribution patterns of the dry and wet species are discussed and it is concluded that habitat diversity offers a better explanation for species numbers and distribution patterns than do island size and isolation. Claims that a dynamic MacArthur-Wilson type equilibrium has been reached for vascular plants in the Galapagos archipelago seem premature.     

Determinants of parasitoid communities of willow‐galling sawflies: habitat overrides physiology,host plant and space

Studies on the determinants of plant–herbivore and herbivore–parasitoid associations provide important insights into the origin and maintenance of global and local species richness. If parasitoids are specialists on herbivore niches rather than on herbivore taxa, then alternating escape of herbivores into novel niches and delayed resource tracking by parasitoids could fuel diversification at both trophic levels. We used DNA barcoding to identify parasitoids that attack larvae of seven Pontania sawfly species that induce leaf galls on eight willow species growing in subarctic and arctic–alpine habitats in three geographic locations in northern Fennoscandia, and then applied distance‐ and model‐based multivariate analyses and phylogenetic regression methods to evaluate the hierarchical importance of location, phylogeny and different galler niche dimensions on parasitoid host use. We found statistically significant variation in parasitoid communities across geographic locations and willow host species, but the differences were mainly quantitative due to extensive sharing of enemies among gallers within habitat types. By contrast, the divide between habitats defined two qualitatively different network compartments, because many common parasitoids exhibited strong habitat preference. Galler and parasitoid phylogenies did not explain associations, because distantly related arctic–alpine gallers were attacked by a species‐poor enemy community dominated by two parasitoid species that most likely have independently tracked the gallers’ evolutionary shifts into the novel habitat. Our results indicate that barcode‐ and phylogeny‐based analyses of food webs that span forested vs. tundra or grassland environments could improve our understanding of vertical diversification effects in complex plant–herbivore–parasitoid networks.     

Microhabitat Segregation of Parapatric Frogs in the Qinling Mountains

Coexistence mechanisms for species with similar ecological traits and overlapping geographic distributions are basic questions in ecology and evolutionary biology. Specific habitat requirements often limit distribution range as well as facilitate partitioning resource utilization in ecological similar species. Understanding niche segregation and differences in microhabitat utilization can contribute to identifying coexistence mechanisms between parapatric species. Feirana quadranus and F. taihangnica are two closely related frog species with parapatric geographic ranges and an elongated contact zone within the Qinling Mountains, which is an important watershed for East Asia. Here, we analysed the difference in microhabitat utilization between the two frog species and explored the key ecological factors that induced their microhabitat differentiation based on quadrats sampled in the contact zone. Our comparison of twenty environmental variables showed that both species used microhabitats with alkalescent warm water and gentle slope conditions. The principal component analysis indicated that climate-related variables, vegetation conditions, and river width were the important factors for microhabitat utilization of these species. These findings contribute to our understanding on the coexistence mechanisms of these two related and parapatric Asian mountain frog species. This study can also be helpful for identifying target habitats to conduct conservation actions and management strategies effectively in the face of environmental changes.     

Geographical variation in macrohabitat use and preferences of the Lesser Spotted Eagle Aquila pomarina

Geographical variation in wildlife–habitat relationships has seldom been studied. We explored macrohabitat use and geographically distinct responses to habitat availability in the Lesser Spotted Eagle Aquila pomarina near the centre (Lithuania) and on the edge (Estonia) of its European distribution range, and in different zones within Estonia. Land cover types and distances to landscape elements, as well as landscape diversity, were measured around 198 Eagle nests and random forest points. Out of six macrohabitat characteristics, two (landscape diversity, area of optimal foraging habitat) showed no geographical variation in use, or preferences by the Eagle. Whereas variation in the use of suboptimal foraging habitats and forests could be attributed to regional differences in their availability, there were geographically distinct preferences for distances between nests and landscape elements. The species avoided anthropogenic edges in Lithuania but tended even to prefer their proximity in Estonia; Eagles selected nest-sites near remote waterbodies throughout Estonia but there was no such preference in Lithuania. The results did not support the hypothesis that latitudinal or range centre-to-periphery gradients existed in habitat relationships of the species; the main factor behind the geographical variation was probably land-use history. In general, the diversity of geographical effects indicated that extrapolating local habitat relationships to other areas may give erroneous results, and large-scale conservation planning regarding species' habitat may be ineffective.     

Habitat Diversity in the Conservation of the Grassland Auchenorrhyncha (Homoptera: Cercopidae,Cicadellidae, Cixidae,Delphacidae) of Northern Britain

Definition of northern British grassland Auchenorrhyncha habitats was carried out using a classification based on analysis of data from 351 sites, involving 121 species, located between Greater Manchester and northern Scotland. Ten habitats were identified showing little influence of geographical position and exhibiting a basic upland-lowland trend. Other factors influencing habitat and species assemblage distribution were soil water, vegetation structure and land cover. An analysis of the species data with satellite-derived land cover data indicated that the lowland covers of tilled land, coast and urban and the upland covers of heath grassland and shrub heath were most important in affecting both species and assemblage distribution. The large-scale survey of grassland sites provided new information on both the ecology and distribution of individual Auchenorrhyncha species. Some were limited to specific habitat types but a considerable number were generalist species found in most or all of the 10 habitat types but showing preferences within upland to lowland or wet to dry site gradients. The ability to generate a subtle grassland Auchenorrhyncha habitat classification with large-scale survey results from standardised and reproducible sampling increases the potential for using habitat diversity for the conservation of grassland Auchenorrhyncha. Habitat preservation would also ensure that species richness (biodiversity) is maintained and that the habitats of rare species are conserved.     

The role of species’ ecological traits in climatically driven altitudinal range shifts of central European birds

Climate change is one of the most important recent forces modulating the structure of ecological communities worldwide. Although a number of studies have documented climatically induced altitudinal range shifts, with species move upwards with increasing temperature and tracking their climatic optima, an examination of interspecific variability in such altitudinal shifts remains unexplored. Using a unique dataset on the altitudinal distribution of birds in a central European mountain range, collected with constant effort and methodology over more than 20 years, we examined the effects of particular species’ ecological traits on interspecific variability in altitudinal range shifts. We predicted that shifts would be greater in species with narrower European climatic niches, breeding in open habitats, feeding on insects and originally breeding at lower altitudes. Patterns of the shifts differed within the time period studied. In the first decade, no climate change was observed and species did not show any direction in their altitudinal shifts. In the second decade, local spring temperatures increased and species moved to higher altitudes. These altitudinal shifts were related to species’ habitat preferences, with open habitat species shifting to higher altitudes than forest species. The effect of other predictors was relatively small. The habitat effects imply either stronger self‐regulation of the forest microclimate compared to open habitats, with forest species less forced to move upwards, or a delayed shift in the alpine timberline due to the slow growth of trees. In the latter case, forest species would face unfavourable climatic conditions and at the same time be constrained by the limited distribution of their habitat. Our study shows that species’ ecology can considerably alter the actual outcome of the impacts of ongoing climate change in mountain areas.     

Assessing conservation values: biodiversity and endemicity in tropical land use systems

Despite an increasing amount of data on the effects of tropical land use on continental forest fauna and flora, it is debatable whether the choice of the indicator variables allows for a proper evaluation of the role of modified habitats in mitigating the global biodiversity crisis. While many single-taxon studies have highlighted that species with narrow geographic ranges especially suffer from habitat modification, there is no multi-taxa study available which consistently focuses on geographic range composition of the studied indicator groups. We compiled geographic range data for 180 bird, 119 butterfly, 204 tree and 219 understorey plant species sampled along a gradient of habitat modification ranging from near-primary forest through young secondary forest and agroforestry systems to annual crops in the southwestern lowlands of Cameroon. We found very similar patterns of declining species richness with increasing habitat modification between taxon-specific groups of similar geographic range categories. At the 8 km(2) spatial level, estimated richness of endemic species declined in all groups by 21% (birds) to 91% (trees) from forests to annual crops, while estimated richness of widespread species increased by +101% (trees) to +275% (understorey plants), or remained stable (-2%, butterflies). Even traditional agroforestry systems lost estimated endemic species richness by -18% (birds) to -90% (understorey plants). Endemic species richness of one taxon explained between 37% and 57% of others (positive correlations) and taxon-specific richness in widespread species explained up to 76% of variation in richness of endemic species (negative correlations). The key implication of this study is that the range size aspect is fundamental in assessments of conservation value via species inventory data from modified habitats. The study also suggests that even ecologically friendly agricultural matrices may be of much lower value for tropical conservation than indicated by mere biodiversity value.     

Habitat preferences of ungulates in closed savanna of central Africa

Habitat preferences of fifteen species of ungulate were studied between July and September 1975 in dry savanna woodland of Mwabvi Game Reserve, Southern Malawi, Central Africa. Thirteen vegetation types were recognized using vegetation transects and plotless sampling techniques (but three of these are omitted from further analysis here either because of the difficulty of sampling in a representative manner or because of their infrequency). A combination of six methods was used to study habitat preferences since each had particular advantages or disadvantages, although quadrat sampling of fresh pellets/spoor counts was the most satisfactory and so used predominantly. The most common and widely distributed species was the Greater kudu, although abundance estimates in different habitats varied according to the method used. Pellet/spoor counts showed heavy use of open grassland by kudu which was not detected by daytime drives. Temporal patterns of activity indicated that the species was moving into more closed woodland during the day and only coming out into open grassland at night. Relative abundance estimates of a species may also be affected by changing group size. The mean group size of kudu increased in more open vegetation, although group size in warthog did not show this relationship. Some species, e.g. impala, reedbuck, and klipspringer showed narrow habitat preferences, occurring in only one or a few vegetation types, whilst others, e.g. kudu, sable, duiker, suni, and grysbok showed much broader preferences. Mixed Colophospermum mopane /Acacia woodland had the highest species diversity but rather low abundance. Open grassland and Acacia/Albizia woodland had high species diversity together with the greatest abundance of ungulates. Open Julbernardia/Diplorynchus, Brachystegia/Julber-nardia woodland, and particularly Pterocarpus/Diplorynchus/Combretum hill woodland had the lowest species diversity and abundance of ungulates. Ready access to cover and availability of suitable food plants probably account for the preferences of certain vegetation types over others, whilst the different behavioural ecology and food preferences of each species account for individual species differences. Access to water probably also determines habitat preferences in particular species, and studies during the wet season may show different distributions.