Life in proto‐Amazonia: Middle Miocene mammals from the Fitzcarrald Arch (Peruvian Amazonia)

The Middle Miocene has been identified as a time of great diversification in modern lineages now distributed in tropical South America, and when basic archetypal traits defining Amazonia appear, including climatic humid conditions, basic floral physiognomy and phylogenetic composition of modern rainforests. Nonetheless, Middle Miocene localities in South America are poorly known, especially at low latitudes where only one species‐rich locality, La Venta in Colombia, has been extensively studied. The present contribution describes the mammal fauna of Fitzcarrald, a new Middle Miocene local fauna from western Amazonia in Peru. Fitzcarrald is correlated with the Laventan South American Land Mammal Age based on the presence of taxa defining the ‘Miocochilius assemblage zone’ in La Venta. The mammalian fauna of Fitzcarrald comprises 24 taxa among cingulates, folivores, astrapotheres, notoungulates, litopterns, rodents, odontocetes and a possible marsupial. At this time, tropical South America was characterized by the presence of the Pebas megawetland, a huge lacustrine complex that provided unique ecological and environmental conditions most likely isolating northern South America from southern South America. These isolating conditions might have come to an end with its disappearance in the Late Miocene and the establishment of the subsequent Acre system, the predecessor fluvial system of modern Amazonia. Results of faunistic similarity between Fitzcarrald and other Miocene faunas throughout South America support these scenarios. The Fitzcarrald mammal fauna exhibits first appearance datums and last appearance datums of various taxa, showing that tropical South America has played a crucial role in the evolutionary history and biogeography of major clades, and revealing a more complex biological history than previously proposed, based on the record from the southern cone of the continent.     

Continental and regional ranges of North American mammals: Rapoport's rule in real and null worlds

Aim To assess the relationship between species richness and distribution within regions arranged along a latitudinal gradient we use the North American mammalian fauna as a study case for testing theoretical models. Location North America. Methods We propose a conceptual framework based on a fully stochastic mid‐domain model to explore geographical patterns of range size and species richness that emerge when the size and position of species ranges along a one‐dimensional latitudinal gradient are randomly generated. We also analyse patterns for the mammal fauna of North America by comparing empirical results from a biogeographical data base with predictions based on randomization null models. Results We confirmed the validity of Rapoport's rule for the mammals of North America by documenting gradients in the size of the continental ranges of species. Additionally, we demonstrated gradients of mean regional range size that parallel those of continental range. Our data also demonstrated that mean range size, measured both as a continental or a regional variable, is significantly correlated with the geographical pattern in species richness. All these patterns deviated sharply from null models. Main conclusions Rapoport's statement of an areographic relationship between species distribution and richness is highly relevant in modern discussions about ecological patterns at the geographical scale.     

The species diversity, distributionand conservation of Namibian mammals

Namibia's extant mammal fauna of 250 species represents about 75% of the southern African region's species richness, 83% of generic richness and 98% of familial richness. Fourteen species are presently recognized as endemic (75% or more of the global population occurring within Namibian borders). These endemics occur in the Namib Desert, pro-Namib transition zone and adjoining escarpment, and are primarily rupicolous. The Namibian endemic mammal fauna is characterized by the monotypic Petromuridae, and the rodent genera Gerbillurus and Petromyscus. The distribution of smaller species has probably not changed significantly over the past 200 years, but species such as lion and plain zebra have undergone range reductions of 95% or more, and five species are listed as recently extinct. Approximately 50% of all Namibian mammal species are provisionally listed as 'secure'. However, due to patchy data, 94 species (38%) are classified as under possible or probable threat. Nineteen species (8%) are classified as under definite threat. Over 13% of Namibia is set aside by the state for conservation purposes. Ninety-five percent of mammal species occur in at least one park, over 80% occur in three or more parks, and 59 species (28%) occur in ten or more parks, although for most species nothing is known of their population viability there. Major threats to mammals in Namibia are invasive aliens, including the risk of genetic pollution, and habitat alteration, especially wetland degradation.     

Effects of small‐scale grassland fragmentation and frequent mowing on population density and species diversity of orthopterans: a long‐term study

Abstract 1. Habitat fragmentation is considered one of the major threats to invertebrate diversity in semi‐natural grassland. However, the effects of habitat fragmentation through mowing on the rich insect fauna of these grasslands have not been sufficiently investigated and experiments are especially rare. 2. We studied the impact of small‐scale grassland fragmentation on orthopterans over 7 years in an experiment which allowed us to additionally investigate the effect of frequent mowing on Orthoptera communities. 3. Overall, Orthoptera density and species richness increased over time. This was likely a result of increased small‐scale habitat heterogeneity and the provision of a short‐turf habitat suitable for xerophilous species. The fragmentation affected orthopteran density and species composition but not species richness whose response lagged behind the changes in abundance. 4. Responses differed between suborders. Ensifera density was higher in fragment than in control plots. Caelifera density did not differ between fragment and control plots. The mown matrix was an unsuitable habitat for most of the species, particularly within the Ensifera. 5. Our experiment shows that even small‐scale fragmentation can affect Orthopteran communities and that the effects became more pronounced over time. As the mown matrix was unsuitable for many Ensifera species, they may go locally extinct when large areas are mown simultaneously.     

Mammals of the northern Philippines: tolerance for habitat disturbance and resistance to invasive species in an endemic insular fauna

Aim Island faunas, particularly those with high levels of endemism, usually are considered especially susceptible to disruption from habitat disturbance and invasive alien species. We tested this general hypothesis by examining the distribution of small mammals along gradients of anthropogenic habitat disturbance in northern Luzon Island, an area with a very high level of mammalian endemism. Location Central Cordillera, northern Luzon Island, Philippines. Methods  Using standard trapping techniques, we documented the occurrence and abundance of 16 endemic and two non‐native species along four disturbance gradients where habitat ranged from mature forest to deforested cropland. Using regression analysis and AIC_c for model selection, we assessed the influence of four predictor variables (geographic range, elevational range, body size and diet breadth) on the disturbance tolerance of species. Results Non‐native species dominated areas with the most severe disturbance and were rare or absent in mature forest. Native species richness declined with increasing disturbance level, but responses of individual species varied. Elevational range (a measure of habitat breadth) was the best predictor of response of native species to habitat disturbance. Geographic range, body size and diet breadth were weakly correlated. Main conclusions The endemic small mammal fauna of northern Luzon includes species adapted to varying levels of natural disturbance and appears to be resistant to disruption by resident alien species. In these respects, it resembles a diverse continental fauna rather than a depauperate insular fauna. We conclude that the long and complex history of Luzon as an ancient member of the Philippine island arc system has involved highly dynamic ecological conditions resulting in a biota adapted to changing conditions. We predict that similar responses will be seen in other taxonomic groups and in other ancient island arc systems.     

The importance of considering both taxonomic and habitat guild approaches in small mammal research

Studies on the effects of habitat fragmentation on small mammals often lead to confounding results as they only consider taxonomic groups in their analysis and neglect functional diversity of the communities. Here we describe the structure and composition of small mammal communities at 22 sites, ranging from 41 to 7035 ha, in a hyper‐fragmented landscape of an Amazonia‐Cerrado ecotone. Also, in considering a taxonomic and habitat guild approach, we report the effects of habitat structures and patch spatial attributes on richness, abundance and species composition. Small mammal richness reported in southern Amazonia (N = 23 species) is greater than most previous studies in the tropics. All rare small mammals captured in this study were forest interior species. Richness of forest interior species was positively related to larger patches, as shown by the species–area relationship. However, 52% of the small mammal species were in forest fragments smaller than 50 ha, highlighting the importance of preserving both large and small forest fragments in a landscape with accelerated habitat reduction. Richness of edge‐tolerant species was not associated with the tested variables, yet edge‐tolerant species were more abundant in degraded environments. Marsupials were positively associated with vertical habitat structures, while rodents were more strongly related to a ground‐level habitat structure. The landscape studied is extremely variable and has contributed to the difficulty in detecting clear patterns, particularly when considering only one approach. Because of the complementary outputs when analysing either taxonomic groups or habitat guilds, we recommend the use of multi‐taxa studies of different guilds to assist decision makers in designing conservation strategies and appropriate management of small mammal populations.     

Rethinking patch size and isolation effects: the habitat amount hypothesis

I challenge (1) the assumption that habitat patches are natural units of measurement for species richness, and (2) the assumption of distinct effects of habitat patch size and isolation on species richness. I propose a simpler view of the relationship between habitat distribution and species richness, the ‘habitat amount hypothesis’, and I suggest ways of testing it. The habitat amount hypothesis posits that, for habitat patches in a matrix of non‐habitat, the patch size effect and the patch isolation effect are driven mainly by a single underlying process, the sample area effect. The hypothesis predicts that species richness in equal‐sized sample sites should increase with the total amount of habitat in the ‘local landscape’ of the sample site, where the local landscape is the area within an appropriate distance of the sample site. It also predicts that species richness in a sample site is independent of the area of the particular patch in which the sample site is located (its ‘local patch’), except insofar as the area of that patch contributes to the amount of habitat in the local landscape of the sample site. The habitat amount hypothesis replaces two predictor variables, patch size and isolation, with a single predictor variable, habitat amount, when species richness is analysed for equal‐sized sample sites rather than for unequal‐sized habitat patches. Studies to test the hypothesis should ensure that ‘habitat’ is correctly defined, and the spatial extent of the local landscape is appropriate, for the species group under consideration. If supported, the habitat amount hypothesis would mean that to predict the relationship between habitat distribution and species richness: (1) distinguishing between patch‐scale and landscape‐scale habitat effects is unnecessary; (2) distinguishing between patch size effects and patch isolation effects is unnecessary; (3) considering habitat configuration independent of habitat amount is unnecessary; and (4) delineating discrete habitat patches is unnecessary.     

Drivers of moth species richness on tropical altitudinal gradients: a cross-regional comparison

Aims We examine the role of species–area relationships (SARs), climatic parameters and phylogeny in shaping the altitudinal species richness patterns of moths. With respect to SARs, we investigate whether habitat heterogeneity is a probable mechanism for mediating area effects. We investigate the consistency of patterns by comparing several discrete regions. Location Nine mountainous regions in tropical Asia and the Malay Archipelago. Methods Presence‐only records for 292 species of the Lepidopteran family Sphingidae were used to measure interpolated species richness in 200‐m altitudinal bands. Species richness was correlated with area measures, which were calculated from both two‐dimensional map projections and three‐dimensional digital elevation models (DEMs). We used data simulations of homogeneous communities to test for effects of sample (i.e. habitat) heterogeneity as a mechanism causing SARs. Species richness patterns were compared among regions and between the two major sphingid clades, and were related to regional climatic characteristics. Results The area of altitudinal bands was a strong (statistical) explanation of species richness, particularly if area was calculated from three‐dimensional DEMs, but SARs often over‐predict species richness in lowland areas. There was no evidence for habitat heterogeneity as a mechanism of altitudinal SARs (tested for Borneo only). Species richness patterns varied considerably between the nine regions, which may, as an alternative to SARs, be explained by climatic differences such as (temperature) seasonality. Phylogenetic clades differed in species richness patterns exhibited. Main conclusion SARs provide strong empirical explanations for (regional) altitudinal patterns of species richness, but lack of evidence for the most likely mechanism cautions against a priori ‘corrections’ of species richness data for area. Furthermore, SARs are often not a sufficient explanation for the drop in species richness towards lowlands. Climate, or other collinear variables, may offer alternative explanations for altitudinal SARs. More research is needed to understand the mechanisms for SARs in an altitudinal context in order to evaluate their importance in the face of parameter collinearity.     

Factors shaping the range-size frequency distribution of the endemic fish fauna of the Tropical Eastern Pacific

Aim To assess the effect of habitat fragmentation and isolation in determining the range‐size frequency distribution (RFD) of the shorefish fauna endemic to a discrete biogeographical region. Location The Tropical Eastern Pacific (TEP). Methods Habitat isolation represents the separation between oceanic islands and the continental shore of the TEP and habitat fragmentation the degree of spatial continuity of habitats (i.e. reefs, soft bottom, nearshore waters) along the continental coast of the TEP. The effects of habitat isolation and fragmentation were quantified by comparing the RFDs of (1) the species found on oceanic islands vs. the continental shore, and (2) species on the continental shore that use different habitat types. Results The RFD of the entire TEP fauna was bimodal, with peaks at both small‐ and large‐range ends of the spectrum. The small‐range peak was due almost entirely to island species and the large‐range peak due mainly to species found in both the continental shore and oceanic islands. RFDs varied among species using different habitats on the continental shore: reef‐fishes had a right‐skewed RFD, soft‐bottom species a flat RFD, and coastal‐pelagic fishes a left‐skewed RFD. Main conclusions Variation in dispersal capabilities associated with habitat isolation and fragmentation in the TEP appears to be the main mechanism contributing to differences among RFD structure, although variation in tolerances arising from the dynamic regional environment may contribute to some patterns. Because diversity patterns are strongly affected by RFD structure, it is now evident that the insular and continental components of a fauna should be treated separately when analysing such patterns. Furthermore, contrasts in RFD structure among species using different habitats demonstrate that a full understanding of the causes of diversity patterns requires analyses of complete regional faunas in relation to regional geography.     

Effects of reduced‐impact logging on physical habitat and fish assemblages in streams of Eastern Amazonia

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Mediterranean v. continental small mammal communities and the environmental degradation of the Dinaric Alps

In order to test for the existence of distinct, regionally-based small mammal faunas, distributional patterns were examined in thirty one species of small mammals (insectivores and rodents) inhabiting the Dinaric Alps (western Balkans). The small mammal fauna was found to consist of three groups: a group of ‘generalist’ species that occurred throughout the study area, plus distinct coastal and continental small mammal assemblages. The continental small mammal assemblage is considerably more species-rich, whilst that of the coastal zone is largely restricted to generalists and species with geophilic or fossorial life-styles (many of which are also commensal with humans). The two assemblages appear to be associated with different vegetation types, and the transition between them lies on the coastal slopes of the Dinaric Alps at c. 700–900 m of altitude. We discuss possible determinants of assemblage composition and species richness, and particularly the possible role of prehistoric environmental degradation in the context of the reduced species-richness of the coastal zone.     

Cumulative effects of land use,altered fire regime and climate change on persistence of Ceanothus verrucosus,a rare,fire‐dependent plant species

Mediterranean ecosystems are among the highest in species richness and endemism globally and are also among the most sensitive to climate and land‐use change. Fire is an important driver of ecosystem processes in these systems; however, fire regimes have been substantially changed by human activities. Climate change is predicted to further alter fire regimes and species distributions, leading to habitat loss and threatening biodiversity. It is currently unknown what the population‐level effects of these landscape‐level changes will be. We linked a spatially explicit stochastic population model to dynamic bioclimate envelopes to investigate the effects of climate change, habitat loss and fragm entation and altered fire regime on population abundances of a long‐lived obligate seeding shrub, Ceanothus verrucosus, a rare endemic species of southern California. We tested a range of fire return intervals under the present and two future climate scenarios. We also assessed the impact of potential anthropogenic land‐use change by excluding land identified as developable by local governments. We found that the 35–50 year fire return interval resulted in the highest population abundances. Expected minimum population abundance (EMA) declined gradually as fire return interval increased, but declined dramatically for shorter fire intervals. Simulated future development resulted in a 33% decline in EMA, but relatively stable population trajectories over the time frame modeled. Relative changes in EMA for alternative fire intervals were similar for all climate and habitat loss scenarios, except under the more severe climate scenario which resulted in a change in the relative ranking of the fire scenarios. Our results show climate change to be the most serious threat facing obligate seeding shrubs embedded in urban landscapes, resulting in population decline and increased local extirpation, and that likely interactions with other threats increase risks to these species. Taking account of parameter uncertainty did not alter our conclusions.     

An empirical evaluation of the African elephant as a focal species for connectivity planning in East Africa

Aim Large, charismatic and wide‐ranging animals are often employed as focal species for prioritizing landscape linkages in threatened ecosystems (i.e. ‘connectivity conservation’), but there have been few efforts to assess empirically whether focal species co‐occur with other species of conservation interest within potential linkages. We evaluated whether the African elephant (Loxodonta africana), a world‐recognized flagship species, would serve as an appropriate focal species for other large mammals in a potential linkage between two major protected area complexes. Location A 15,400 km² area between the Ruaha and Selous ecosystems in central Tanzania, East Africa. Methods We used walking transects to assess habitat, human activity and co‐occurrence of elephants and 48 other large mammal species (> 1 kg) at 63 sites using animal sign and direct sightings. We repeated a subset of transects to estimate species detectability using occupancy modelling. We used logistic regression and AIC model selection to characterize patterns of elephant occurrence and assessed correlation of elephant presence with richness of large mammals and subgroups. We considered other possible focal species, compared habitat‐based linear regression models of large mammal richness and used circuit theory to examine potential connectivity spatially. Results Elephants were detected in many locations across the potential linkage. Elephant presence was highly positively correlated with the richness of large mammals, as well as ungulates, carnivores, large carnivores and species > 45 kg in body mass (‘megafauna’). Outside of protected areas, both mammal richness and elephant presence were negatively correlated with human population density and distance from water. Only one other potential focal species was more strongly correlated with species richness than elephants, but detectability was highest for elephants. Main conclusions Although African elephants have dispersal abilities that exceed most other terrestrial mammals, conserving elephant movement corridors may effectively preserve habitat and potential landscape linkages for other large mammal species among Tanzanian reserves.     

Habitat fragmentation and species richness

In a recent article in this journal, Fahrig (2013, Journal of Biogeography, 40 , 1649–1663) concludes that variation in species richness among sampling sites can be explained by the amount of habitat in the ‘local landscape’ around the sites, while the spatial configuration of habitat within the landscape makes little difference. This conclusion may be valid for small spatial scales and when the total amount of habitat is large, but modelling and empirical studies demonstrate adverse demographic consequences of fragmentation when there is little habitat across large areas. Fragmentation effects are best tested with studies on individual species rather than on communities, as the latter typically consist of species with dissimilar habitat requirements. The total amount of habitat and the degree of fragmentation tend to be correlated, which poses another challenge for empirical studies. I conclude that fragmentation poses an extra threat to biodiversity, in addition to the threat posed by loss of habitat area.     

What is the effect of climate change on marine fish biodiversity in an area of low connectivity,the Baltic Sea?

Aim Climate change could result in an increase in species richness because large‐scale biogeography suggests that more species could be gained from equatorial regions than may be lost pole‐ward. However, the colonization of newly available habitat may lag behind the rate dictated by climatic warming if there exists of a lack of connectivity between ‘donor’ and receiving areas. The objective of this study was to compare how regional warming affected the biodiversity of marine fish in areas that differed in their connectivity in the Baltic Sea. Location North‐east Atlantic, Kattegat and Baltic Sea. Methods The total species richness and the mean species richness from scientific surveys were related to changes in temperature and salinity. Changes in the extent of the distribution of individual fish species were related to the latitudinal distribution, salinity tolerance, maximum body size and exploitation status to assess to what extent climate change and fishing impacts could explain changes in species richness in the Baltic. Results Rising temperatures in the well‐connected Kattegat correlated to an increase in the species richness of fish, due to an increase in low‐latitude species. Unexpectedly, species richness in the poorly connected Baltic Sea also increased. However, the increase seems to be related to higher salinity rather than temperature and there was no influx of low‐latitude species. Main conclusions These results do not support the hypothesis that low‐connectivity areas are less likely to see increases in species richness in response to warming. This indicates that the effect of climate change on biodiversity may be more difficult to predict in areas of low connectivity than in well‐connected areas.     

Prioritising research efforts for effective species conservation: a review of 145 years of koala research

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Responses of Primates to Landscape Change in Amazonian Land‐bridge islands—a Multi‐scale Analysis

Large hydroelectric dams are one of the current drivers of habitat loss across Amazonian forests. We investigated how the primate community at a hydroelectric dam in Brazilian Amazonia responded to changes in the landscape and local habitat structure of land‐bridge islands after 21 yr of post‐isolation history. The Balbina Dam, constructed in 1986, inundated 3129 km² of primary forests and created more than 3500 variable‐sized islands. We conducted primate and habitat structure surveys on 20 islands from 5 to 1815 ha, and extracted forest patch and landscape metrics for each island. The number of primate species per island varied between 0 and 7 species. Primate composition varied substantially according to both island area and forest cover remaining within the landscape, whereas island area alone was the most significant predictor of richness. Locally, tree density and vertical stratification were the most significant explanatory variables of primate composition and richness. A model containing area effects had the most explanatory power regarding site occupancy for most species. Individually, each species responded differently, with howler and brown capuchin monkeys showing greater tolerance to cope with habitat changes. Body size was also an important predictor of primate occupancy. We recommend protecting large fragments and enhancing the suitability of surrounding habitats to ensure primate conservation in most Neotropical fragmented landscapes. Given the flat topography of hydroelectric reservoirs, which mainly favors the formation of small islands, and the escalating hydropower development plans in Amazonia, our findings provide evidence for pervasive detrimental impacts of dams on primate communities.     

Movement Behavior of Native and Invasive Small Mammals Shows Logging May Facilitate Invasion in a Tropical Rain Forest

Invasive species pose one of the greatest threats to biodiversity. This study investigates the extent to which human disturbance to natural ecosystems facilitates the spread of non‐native species, focusing on a small mammal community in selectively logged rain forest, Sabah, Borneo. The microhabitat preferences of the invasive Rattus rattus and three native species of small mammal were examined in three‐dimensional space by combining the spool‐and‐line technique with a novel method for quantifying fine‐scale habitat selection. These methods allowed the detection of significant differences for each species between the microhabitats used compared with alternative, available microhabitats that were avoided. Rattus rattus showed the greatest preference for heavily disturbed habitats, and in contrast to two native small mammals of the genus Maxomys, R. rattus showed high levels of arboreal behavior, frequently leaving the forest floor and traveling through the understory and midstory forest strata. This behavior may enable R. rattus to effectively utilize the complex three‐dimensional space of the lower strata in degraded forests, which is characterized by dense vegetation. The behavioral flexibility of R. rattus to operate in both terrestrial and arboreal space may facilitate its invasion into degraded forests. Human activities that generate heavily disturbed habitats preferred by R. rattus may promote the establishment of this invasive species in tropical forests in Borneo, and possibly elsewhere. We present this as an example of a synergistic effect, whereby forest disturbance directly threatens biodiversity and indirectly increases the threat posed by invasive species, creating habitat conditions that facilitate the establishment of non‐native fauna.     

Local richness and distribution of the lizard fauna in natural habitat mosaics of the Brazilian Cerrado

We investigate local lizard richness and distribution in central Brazilian Cerrado, harbouring one of the least studied herpetofaunas in the Neotropical region. Our results are based on standardized samplings at 10 localities, involving 2917 captures of 57 lizard species in 10 families. Local richness values exceeded most presented in earlier studies and varied from 13 to 28 species, with modal values between 19 and 28 species. Most of the Cerrado lizard fauna is composed of habitat‐specialists with patchy distributions in the mosaic of grasslands, savannas and forests, resulting in habitat‐structured lizard assemblages. Faunal overlap between open and forested habitats is limited, and forested and open areas may act as mutual barriers to lizard distribution. Habitat use is influenced by niche conservatism in deep lineages, with iguanians and gekkotans showing higher use of forested habitats, whereas autarchoglossans are richer and more abundant in open habitats. Contrary to trends observed in Cerrado birds and large mammals, lizard richness is significantly higher in open, interfluvial habitats that dominate the Cerrado landscape. Between‐localities variation in lizard richness seems tied to geographical distance, landscape history and phylogenetic constraints, factors operating in other well‐studied lizard faunas in open environments. Higher richness in dominant, open interfluvial habitats may be recurrent in Squamata and other small‐bodied vertebrates, posing a threat to conservation as these habitats are most vulnerable to the fast, widespread and ongoing process of habitat destruction in central Brazil.