Habitat fragmentation disrupts the demography of a widespread native mammal

Fragmentation theory predicts that population persistence should be positively correlated with the size of habitat fragments. The patterns of occurrence of many species are consistent with this prediction, but the demographic processes that determine how species respond to fragmentation are poorly understood. In addition, habitat quality may interact with fragment size as an influence on demographic performance. We investigated these predictions for the native bush rat Rattus fuscipes by testing the following hypotheses: 1) population performance (i.e. viability as determined by various demographic parameters) is positively correlated with fragment size; and 2) population performance is positively correlated with habitat quality. Populations of R. fuscipes were censused in two large (>49 ha) and eight small (<2.5 ha) forest fragments in an agricultural region of southeastern Australia. Fragments with high and low quality habitat were included in each size category. Fragment size influenced multiple aspects of population demography; populations in large fragments had higher densities, older age structures, received more potential immigrants, and were more likely to recruit adults than those in small fragments. Reproductive patterns were more predictable in large fragments. Habitat quality per se had less marked effects; adult females were heavier and subadults more prevalent in fragments with high quality habitat. However, high quality habitat enhanced population performance in small fragments more so than in large ones. Despite being widespread in the study area, R. fuscipes populations are profoundly impacted by habitat fragmentation, with population performance declining with fragment size. Studies based on patterns of species occurrence should be interpreted with caution as they may mask critical processes occurring at the population level. For a thorough understanding of the effects of habitat fragmentation, population‐level studies are required.     

Effects of forest fragmentation on the lekking behavior of White-throated Manakins in Central Amazonia

Forest fragmentation can affect various aspects of population dynamics, but few investigators have assessed possible effects on the behavior of a species. Loss of habitat may limit population recruitment and abundance, which may alter breeding dynamics in forest remnants. We examined the lekking behavior of White-throated Manakins (Corapipo gutturalis) in a fragmented landscape to determine if forest fragmentation affected the spatial distribution of display courts and male behavior at courts. We captured and observed males at 19 courts located in 11 primary forests of different sizes in forest habitats of the Biological Dynamics of Forest Fragments Project area, an experimentally fragmented landscape located in the central Brazilian Amazon, and estimated their spatial distribution as the distance to the nearest court in the landscape. We quantified habitat loss using the proportion of forest cover surrounding courts and their distances to forest edges. No courts were detected in 1-ha forest fragments, suggesting direct effects from habitat loss following fragmentation that affected connectivity and thus recruitment and persistence of courts in the smallest fragments. The spatial distribution of display courts in forests larger than 10 ha remained unaltered, compared to display courts in continuous forests, but adult males were less numerous on courts with a higher percentage of forest cover and they displayed less on courts closer to forest edges. The spatial distribution of courts also contributed to variation in male social behavior, with more juvenile males present and adult males displaying at lower rates at more isolated courts. Although White-throated Manakins are locally common, the observed behavioral changes in response to habitat loss may affect their population dynamics. Our results show the importance of assessing behavioral changes in conservation programs and, in particular, of including biologically relevant measures of habitat loss in addressing its possible effects on species persistence in fragmented landscapes.     

Role of movement,interremnant dispersal and edge effects in determining sensitivity to habitat fragmentation in two forest‐dependent rodents

Abstract Habitat fragmentation and disturbance affect patterns of habitat use, animal movement and spatial behaviour and might have significant effects upon population dynamics and trends, and ultimately population persistence. Previous studies have suggested that the ability to disperse between remnants and a positive or neutral response to edges should be associated with species capable of persisting in remnant habitat. Using both radiotracking and trapping data, movement patterns, dispersal and response to habitat edges of Rattus fuscipes were examined within forests, corridors, remnants and pastures in south‐east Queensland, Australia. Rattus fuscipes has previously been shown to be robust to the effects of habitat fragmentation; however, contrary to expectations, R. fuscipes was found to be sensitive to edges, and no evidence of interremnant dispersal was detected, despite interremnant distances that were substantially smaller than the distances R. fuscipes was found to move in continuous habitat. Using only trapping data, the same factors were examined in relation to Melomys cervinipes, a species sensitive to fragmentation. Melomys cervinipes was found to utilize edge habitat, but no evidence of interremnant dispersal was detected, although the capacity to detect such movement was limited by low abundance in remnants where M. cervinipes was extant, and the species absence from many remnants. Movement patterns, interremnant dispersal capacity, and sensitivity to edges did not prove to be good predictors of these species responses to habitat fragmentation. Alternative explanations, such as population fluctuation and the capacity for rapid population growth in remnants for these two species, and the influence habitat quality has on these parameters should be investigated.     

Patch occupancy and abundance of local populations in landscapes differing in degree of habitat fragmentation: a case study of the colonial black‐headed gull,Chroicocephalus ridibundus

Aim This study investigated whether habitat fragmentation at the landscape level influences patch occupancy and abundance of the black‐headed gull, Chroicocephalus ridibundus, and whether the response of the species to environmental factors is consistent across replicated landscape plots. Location Water bodies (habitat patches) in southern Poland. Methods Surveys were conducted in two landscape types (four plots in each): (1) more‐fragmented landscape, in which habitat patches were small (mean size 2.2–6.2 ha) and far apart (mean distance 2.5–3.1 km); and (2) less‐fragmented landscape, in which habitat patches were large (mean size 9.2–16.5 ha) and separated by short distances (mean 0.9–1.4 km). Observations were performed twice in 284 potential habitat patches during the 2007 breeding season. Results Colonies were significantly more frequent and larger in the less‐fragmented landscapes than in the more‐fragmented ones. Probability of patch occupancy and number of breeding birds were positively related with patch size and these relationships were especially strong in the more‐fragmented landscapes. In the less‐fragmented landscapes, the occurrence of black‐headed gulls was negatively related to the distance to the nearest local population, but in the more‐fragmented landscapes such a relationship was not detected. As distance to the nearest habitat patch increased, the probability of the patch occupancy decreased in the more‐fragmented landscapes. Moreover, abundance was negatively influenced by distance to the nearest habitat patch, especially strongly in more‐fragmented landscapes. Proximity of corridors (rivers) positively influenced the occupation of patches regardless of landscape type. The number of islets positively influenced occupancy and abundance of local populations, and this relationship was stronger in the more‐fragmented landscapes. Main conclusions Our results are in agreement with predictions from metapopulation theory and are the first evidence that populations of black‐headed gulls may have a metapopulation structure. However, patch occupancy and abundance were differentially affected by explanatory variables in the more‐fragmented landscapes than in the less‐fragmented ones. This implies that it is impossible to derive, a priori, predictions about presence/abundance patterns based on only a single landscape.     

Landscape‐level tree cover predicts species richness of large‐bodied frugivorous birds in forest fragments

Large‐bodied frugivorous birds play an important role in dispersing large‐sized seeds in Neotropical rain forests, thereby maintaining tree species richness and diversity. Conversion of contiguous forest land to forest fragments is thought to be driving population declines in large‐bodied frugivores, but the mechanistic drivers of this decline remain poorly understood. To assess the importance of fragment‐level versus local landscape attributes in influencing the species richness of large‐bodied (>100 g) frugivorous birds, we surveyed 15 focal species in 22 forest fragments (2.7 to 33.6 ha, avg. = 16.0 ha) in northwest Ecuador in 2014. Fragment habitat variables included density of large trees, canopy openness and height, and fragment size; landscape variables included elevation and the proportion of tree cover within a 1 km radius of each fragment. At both the individual species level, and across the community of 12 species of avian frugivore we detected, there was higher richness and probability of presence in fragments with more tree cover on surrounding land. This tendency was particularly pronounced among some endangered species. These findings corroborate the idea that partially forested land surrounding fragments may effectively increase the suitable habitat for forest‐dwelling frugivorous birds in fragmented landscapes. These results can help guide conservation priorities within fragmented landscapes, with particular reference to retaining trees and reforesting to attain high levels of tree cover in areas between forest patches.     

Movements of four native Hawaiian birds across a naturally fragmented landscape

Animals often increase their fitness by moving across space in response to temporal variation in habitat quality and resource availability, and as a result of intra and inter‐specific interactions. The long‐term persistence of populations and even whole species depends on the collective patterns of individual movements, yet animal movements have been poorly studied at the landscape level. We quantified movement behavior within four native species of Hawaiian forest birds in a complex lava‐fragmented landscape: Hawai?i ‘amakihi Chlorodrepanis virens, ‘oma‘o Myadestes obscurus, ‘apapane Himatione sanguinea, and ‘i‘iwi Drepanis coccinea. We evaluated the relative importance of six potential intrinsic and extrinsic drivers of movement behavior and patch fidelity: 1) forest fragment size, 2) the presence or absence of invasive rats (Rattus sp.), 3) season, 4) species, 5) age, and 6) sex. The study was conducted across a landscape of 34 forest fragments varying in size from 0.07 to 12.37 ha, of which 16 had rats removed using a treatment‐control design. We found the largest movements in the nectivorous ‘apapane and ‘i‘iwi, intermediate levels in the generalist Hawai?i ‘amakihi, and shortest average movement for the ‘oma‘o, a frugivore. We found evidence for larger patch sizes increasing patch fidelity only in the ‘oma‘o, and an effect of rat‐removal increasing patch fidelity of Hawai?i ‘amakihi only after two years of rat‐removal. Greater movement during the non‐breeding season was observed in all species, and season was an important factor in explaining higher patch fidelity in the breeding season for ‘apapane and ‘i‘iwi. Sex was important in explaining patch fidelity in ‘oma‘o only, with males showing higher patch fidelity. Our results provide new insights into how these native Hawaiian species will respond to a changing environment, including habitat fragmentation and changing distribution of threats from climate change.     

Howler monkey tolerance to habitat shrinking: Lifetime warranty or death sentence?

Habitat loss and fragmentation are major threats to the conservation of nonhuman primates. Given that species differ in their responses to fragmented landscapes, identifying the factors that enable them to cope with altered environments or that cause their extirpation is critical to design conservation management strategies. Howler monkeys (Alouatta spp.) are good models for studying the strategies of tolerant arboreal taxa and how they cope with spatial restriction, because they live in habitats ranging from vast pristine forests to small disturbed fragments and orchards. While some aspects of their ecology and behavior are conserved, others vary in predictable ways in response to habitat shrinking and decreasing resource availability. We argue that the ability of individual howler monkeys to inhabit low-quality environments does not guarantee the long-term persistence of the small populations that live under these conditions. Their local extirpation explains why few forest fragments below a given area threshold are frequently inhabited in landscapes where recolonization and gene flow are compromised by long isolation distances or less permeable matrices. In sum, howlers’ ability to cope with habitat restriction at the individual level in the short-term may mask the inevitable fate of isolated populations, thereby compromising the persistence of the species at a regional scale in the long-term if howlers’ need for protection in large forests is undervalued.     

Seed-dispersal distributions by trumpeter hornbills in fragmented landscapes

Frugivorous birds provide important ecosystem services by transporting seeds of fleshy fruited plants. It has been assumed that seed-dispersal kernels generated by these animals are generally leptokurtic, resulting in little dispersal among habitat fragments. However, little is known about the seed-dispersal distribution generated by large frugivorous birds in fragmented landscapes. We investigated movement and seed-dispersal patterns of trumpeter hornbills (Bycanistes bucinator) in a fragmented landscape in South Africa. Novel GPS loggers provide high-quality location data without bias against recording long-distance movements. We found a very weakly bimodal seed-dispersal distribution with potential dispersal distances up to 14.5 km. Within forest, the seed-dispersal distribution was unimodal with an expected dispersal distance of 86 m. In the fragmented agricultural landscape, the distribution was strongly bimodal with peaks at 18 and 512 m. Our results demonstrate that seed-dispersal distributions differed when birds moved in different habitat types. Seed-dispersal distances in fragmented landscapes show that transport among habitat patches is more frequent than previously assumed, allowing plants to disperse among habitat patches and to track the changing climatic conditions.     

Habitat use and dispersal characteristic by <Emphasis Type="Italic">Stethophyma grossum</Emphasis>: the role of habitat isolation and stable habitat conditions towards low dispersal

Species in a highly fragmented environment, such as the intensively used agricultural landscapes of Europe, are expected to be in danger of extinction. We hypothesize according to Kisdi’s theory (Am Nat 159:579–596, 2002) that species in fragmented landscapes with isolated habitats in general tend to possess low dispersal. In order to verify this hypothesis we studied the movement patterns of Stethophyma grossum, a hygrophilous species of wetlands, by mark–release–recapture techniques in a landscape with scattered suitable habitats over 3 years. The study focused on the major population in this landscape (site #1) as dispersal behaviour was assumed to be greatest. Actually, marked individuals of S. grossum were never found in any further suitable habitats in close vicinity to site #1. Despite that the peatland meadow of study site #1 was all over covered with homogenous vegetation only 6% (1.8 ha) of the whole area (30 ha) were occupied by S. grossum. The mean recapture rate over 3 years amounted to 39% with no significant differences between males and females. Both covered little distances within their mean range size of 1.8 ha; the median distances were 36.91 m for males and 26.65 m for females. We confirm the hypothesis that sub-populations of species in longstanding naturally isolated habitats, which habitat conditions have been stable; evolved low dispersal with little movements which are routine movements to find mating partners or food.     

Ranging Behavior of an Arboreal Marsupial in a Plantation Landscape

Forests are becoming increasingly fragmented, primarily because of their conversion to production landscapes. Animals occupying modified landscapes may need to expand their ranges and move longer distances between remnant forest patches to find resources. The establishment of plantations in fragmented landscapes, however, may provide complementary habitat for wildlife and improve connectivity, reducing the amount of movement required. Our objective was to determine the influence of plantations on koala (Phascolarctos cinereus) habitat use and test 2 competing hypotheses on the relationship between plantations and range size. We deployed global positioning system and very high frequency collars on 40 koalas in 2 landscapes (plantation and non-plantation) in Victoria, Australia. From 68,216 tracking points collected over an 8-month period, we calculated and compared seasonal home range size and habitat use between landscapes. There was no difference in range size, the size and number of core use areas, or the distance between core use areas between plantation and non-plantation landscapes. Plantations extend existing koala habitat and facilitate koala movement through a landscape; however, remnant native vegetation is still more frequently used. Consequently, native vegetation (even fragmented, linear roadside vegetation) is of high conservation importance for the persistence of koalas in modified landscapes. © 2020 The Wildlife Society.     

Sugarcane and Eucalyptus plantation equally limit the movement of two forest‐dependent understory bird species

Habitat fragmentation results in landscape configuration, which affects the species that inhabit it. As a consequence, natural habitat is replaced by different anthropogenic plantation types (e.g. pasture, agriculture, forestry plantations and urban areas). Anthropogenic plantations are important for biodiversity maintenance because some species or functional groups can use it as a complementary habitat. However, depending on plantation permeability, it can act as a barrier to the movement of organisms between habitat patches, such as forest fragments, reducing functional connectivity for many species. Anthropogenic plantations are becoming the most common land use and cover type in the Anthropocene and biodiversity conservation in fragmented landscapes requires information on how different plantation types affect the capacity of the species to move through the landscape. In this study, we evaluated the influence of the type and structure of plantations on the movement of two forest‐dependent understory bird species – plain antvireo (Dysithamnus mentalis) and flavescent warbler (Myiothlyps flaveola) – within a highly fragmented landscape of Atlantic Forest hotspot. Knowing that forestry plantation is assumed to be more permeable to dependent forest bird species than open ones, we selected six study areas containing a forest fragment and surrounding plantation: three with sugarcane plantation and three with Eucalyptus sp. plantation. We used playback calls to stimulate the birds to leave forest fragments and traverse the plantations. Control trials were also carried out inside the forest fragments to compare the distances crossed. We observed that individuals moved longer distances inside forest than between plantation types, which demonstrate that plantations do constrict the movements of both species. The two plantation types equally impeded the movements of the species, suggesting the opposite of the general assumption that forestry plantations are more permeable. Our results indicate that, for generalist species, plantation type does not matter, but its presence negatively impacts movement of these bird species. We highlight that plantations have negative influences on the movements of common bird species, and discuss why this is important when setting conservation priorities.     

Connectivity of prairie dog colonies in an altered landscape: inferences from analysis of microsatellite DNA variation

Connectivity of populations influences the degree to which species maintain genetic diversity and persist despite local extinctions. Natural landscape features are known to influence connectivity, but global anthropogenic landscape change underscores the importance of quantifying how human-modified landscapes disrupt connectivity of natural populations. Grasslands of western North America have experienced extensive habitat alteration, fragmenting populations of species such as black-tailed prairie dogs (Cynomys ludovicianus). Population sizes and the geographic range of prairie dogs have been declining for over a century due to habitat loss, disease, and eradication efforts. In many places, prairie dogs have persisted in the face of emerging urban landscapes that carve habitat into smaller and smaller fragments separated by uninhabitable areas. In extreme cases, prairie dog colonies are completely bounded by urbanization. Connectivity is particularly important for prairie dogs because colonies suffer high probabilities of extirpation by plague, and dispersal permits recolonization. Here we explore connectivity of prairie dog populations using analyses of 11 microsatellite loci for 9 prairie dog colonies spanning the fragmented landscape of Boulder County, Colorado. Isolation-by-resistance modeling suggests that wetlands and high intensity urbanization limit movement of prairie dogs. However, prairie dogs appear to move moderately well through low intensity development (including roads) and freely through cropland and grassland. Additionally, there is a marked decline in gene flow between colonies with increasing geographic distance, indicating isolation by distance even in an altered landscape. Our results suggest that prairie dog colonies retain some connectivity despite fragmentation by urbanization and agricultural development.     

Monitoring movement into and through a newly planted rainforest corridor using genetic analysis of natal origin

Summary Genetic analysis of individual origins works best with populations that are genetically distinct but which exchange a high rate of immigrants, conditions that don’t normally coexist since immigration acts to prevent the accumulation of genetic differences. We provide empirical results from a newly constructed habitat linkage to illustrate the unique suitability of such analysis to monitoring the re‐establishment of connections between previously isolated populations. Donaghy’s Corridor links a previously isolated 498 ha fragment of rainforest to an adjacent 80 000 ha of intact forest. Starting in the final year of the planting programme that established the corridor, we trapped two species of native small mammals, the Bush Rat (Rattus fuscipes) and the Cape York Rat (Rattus leucopus), within and nearby the linkage. We used genetic data from ear clippings to determine which side of the corridor individual animals originated from, and by comparing this information to trap locations, we identified 16 long‐distance movements through the corridor. As genetic analysis of origins allowed movements to be detected from a single capture event and as it reflected movement since birth, this approach yielded considerably more data than capture records alone. The combination of movement and capture records allowed species‐specific assessment of corridor function, revealing that the use and occupation of the corridor was higher for Bush Rat than for Cape York Rat and was neither symmetrical nor uniform. Long‐distance movements through the corridor were most common immediately after habitat restoration, dropping off as the reconstructed habitat was colonized.     

Reptiles and frogs use most land cover types as habitat in a fine‐grained agricultural landscape

Agricultural landscapes comprise much of the earth's terrestrial surface. However, knowledge about how animals use and move through these landscapes is limited, especially for small and cryptic taxa, such as reptiles and amphibians. We aimed to understand the influence of land use on reptile and frog movement in a fine‐grained grazing landscape. We surveyed reptiles and frogs using pitfall and funnel traps in transects located in five land use types: 1) woodland remnants, 2) grazed pastures, 3) coarse woody debris added to grazed pastures, 4) fences in grazed pastures and 5) linear plantings within grazed pastures. We found that the different land cover types influenced the types and distances moved by different species and groups of species. Reptiles moved both within, and out of, grazed paddocks more than they did in woodland remnants. In contrast, frogs exhibited varying movement behaviours. The smooth toadlet (Uperoleia laevigata) moved more often and longer distances within remnants than within paddocks. The spotted marsh frog (Limnodynastes tasmaniensis) moved out of grazed pastures more than out of pastures with coarse woody debris added or fences and were never recaptured in plantings. We found that most recaptured reptiles and frogs (76.3%) did not move between trapping arrays, which added to evidence that they perceived most of the land cover types as habitat. We suggest that even simple fences may provide conduits for movement in the agricultural landscape for frogs. Otherwise, most reptile and frog species used all land cover types as habitat, though of varying quality. Reptiles appeared to perceive the woodland remnants as the highest quality habitat. This landscape is fine‐grained which may facilitate movement and persistence due to high heterogeneity in vegetation cover over short distances. Therefore, intensification and increasing the size of human land use may have negative impacts on these taxa.     

Seed‐dispersal interactions in fragmented landscapes – a metanetwork approach

Mutualistic interactions repeatedly preserved across fragmented landscapes can scale‐up to form a spatial metanetwork describing the distribution of interactions across patches. We explored the structure of a bird seed‐dispersal (BSD) metanetwork in 16 Neotropical forest fragments to test whether a distinct subset of BSD‐interactions may mediate landscape functional connectivity. The metanetwork is interaction‐rich, modular and poorly connected, showing high beta‐diversity and turnover of species and interactions. Interactions involving large‐sized species were lost in fragments < 10 000 ha, indicating a strong filtering by habitat fragmentation on the functional diversity of BSD‐interactions. Persistent interactions were performed by small‐seeded, fast growing plant species and by generalist, small‐bodied bird species able to cross the fragmented landscape. This reduced subset of interactions forms the metanetwork components persisting to defaunation and fragmentation, and may generate long‐term deficits of carbon storage while delaying forest regeneration at the landscape level.     

Habitat patch and matrix effects on small-mammal persistence in Amazonian forest fragments

Tropical forest mammal assemblages are widely affected by the twin effects of habitat loss and habitat fragmentation. We evaluated the effects of forest patch metrics, habitat structure, age of patch isolation, and landscape metrics on the species richness, abundance and composition of small mammals at 23 forest fragments (ranging in size from 43 to 7,035 ha) in a highly deforested 3,609-km² landscape of southwestern Brazilian Amazonia. Using pitfall traps and both terrestrial and arboreal traplines of Sherman, Tomahawk and snap traps, we captured a total of 844 individuals over 34,900 trap-nights representing 26 species and 20 genera of small-mammals, including 13 rodent and 13 marsupial species. We also consider the effects of distance from forest edges on species occupancy and abundance. Overall small mammal abundance, species richness and species composition were primarily affected by the quality of the open-habitat matrix of cattle pastures, rather than by patch metrics such as fragment size. Ultimately, small mammal community structure was determined by a combination of both landscape- and patch-scale variables. Knowledge of the anthropogenic factors that govern small mammal community structure is of critical importance for managing the persistence of forest vertebrates in increasingly fragmented neotropical forest landscapes.     

Gap-crossing movements predict species occupancy in Amazonian forest fragments

In fragmented landscapes, species persistence within isolated habitat patches is governed by a myriad of species life‐history, habitat patch and landscape characteristics. We investigated the inter‐specific variation in non‐forest gap‐crossing abilities of an entire tropical forest‐dependent avifauna. We then related this measure of dispersal ability to species life‐history characteristics and occupancy data from 31 variable‐sized forest patches sampled within the same fragmented forest landscape. A total of 5436 gap‐crossing movements of 231 forest‐dependent bird species were observed across ten linear forest gaps of varying widths, adjacent to large areas of undisturbed forest. Species persistence in isolated fragments was strongly linked to gap‐crossing ability. The most capable gap‐crossers were medium to large‐bodied species in the large insectivore, frugivore and granivore guilds, matching the most prevalent subset of species in small forest patches. However, some competent gap‐crossing species failed to occur in small patches, and minimum forest‐patch area requirements were more important in determining patch occupancy for these species. Narrow forest gaps (4–70 m) created by roads and power‐lines may become territory boundaries, thereby eliminating home‐range gap‐crossing movements for many forest species, but permit rarer dispersal events. Wider gaps (>70 m) may inhibit gap‐crossing behaviour for all but the most vagile species. Although patch size and quality may be the most important factors in structuring species assemblages in forest fragments, our results show that the degree of patch isolation and permeability of the surrounding matrix also explain which species can persist in forest isolates. Reducing the number and width of forest‐dividing gaps; maintaining and/or creating forest corridors and increasing matrix permeability through the creation and maintenance of ‘stepping‐stone’ structures will maximise the species retention in fragmented tropical forest landscapes.     

Relative importance of quantity, quality and isolation of patches for butterfly diversity in fragmented urban forests

The majority of forests in urban areas are small and isolated. Improving habitat quality of small forests instead of increasing habitat size and connectivity could be an effective means of conserving the biodiversity of such highly fragmented landscapes. In this study, we investigated the relative importance of habitat quantity, quality and isolation on butterfly assemblages in urban fragmented forests in Tokyo, Japan. We used four habitat geographic parameters: (1) fragment size, (2) shape index, (3) isolation (distance to the mainland), and (4) connectivity; and three habitat quality parameters: (1) herbaceous nectar plant abundance, (2) herbaceous nectar plant diversity, and (3) larval host plant diversity. We surveyed butterfly assemblages along transects in 20 forest fragments that ranged in size from 1 to 122 ha. We used generalized linear models to relate the number of species in a fragment to four habitat geographic parameters and three habitat quality parameters. The averaged models based on AIC_c showed that fragment size had a strong positive effect on butterfly species richness. There was also a positive effect of herbaceous nectar plant abundance on species diversity. These findings suggest that improving the habitat quality of small and isolated forests in highly fragmented landscapes may be capable of maintaining levels of butterfly diversity comparable to those of large fragments.     

Using landscape history to predict biodiversity patterns in fragmented landscapes

Landscape ecology plays a vital role in understanding the impacts of land‐use change on biodiversity, but it is not a predictive discipline, lacking theoretical models that quantitatively predict biodiversity patterns from first principles. Here, we draw heavily on ideas from phylogenetics to fill this gap, basing our approach on the insight that habitat fragments have a shared history. We develop a landscape ‘terrageny’, which represents the historical spatial separation of habitat fragments in the same way that a phylogeny represents evolutionary divergence among species. Combining a random sampling model with a terrageny generates numerical predictions about the expected proportion of species shared between any two fragments, the locations of locally endemic species, and the number of species that have been driven locally extinct. The model predicts that community similarity declines with terragenetic distance, and that local endemics are more likely to be found in terragenetically distinctive fragments than in large fragments. We derive equations to quantify the variance around predictions, and show that ignoring the spatial structure of fragmented landscapes leads to over‐estimates of local extinction rates at the landscape scale. We argue that ignoring the shared history of habitat fragments limits our ability to understand biodiversity changes in human‐modified landscapes.     

Movement Patterns of Frugivorous Birds Promote Functional Connectivity among Chaco Serrano Woodland Fragments in Argentina

Movement patterns of frugivorous birds may be altered in anthropogenically fragmented landscapes, with possible consequences for seed dispersal and plant recruitment. We studied the movement patterns and functional connectivity of six frugivorous bird species (Colaptes melanochloros, Thraupis bonariensis, Pitangus sulphuratus, Saltator aurantiirostris, Turdus amaurochalinus, and Elaenia spp.) in a fragmented Chaco‐woodland landscape in Argentina. We recorded the directions of bird movements (arrivals and departures) and whether their destination was oriented toward a specific neighboring fragment. We evaluated the movement rates, distance of interpatch movement, and functional connectivity within the landscape for the six bird species. We applied a novel approach, graph theory, to represent bird movement patterns in the landscape and the functional connections among fragments for each bird species. Bird movements were recorded at point‐count stations established along the edges of each fragment. The directions of arrival and departure movements from and to neighboring fragments revealed complex movement patterns. However, the destination of bird movements after leaving the focal fragments was usually concentrated on only a few neighboring fragments of different sizes. Pitangus sulphuratus and T. bonariensis showed larger movement rates and higher functional connectivity (number of graphs and functional area) than the other frugivorous species. The functional connectivity mediated by movement of frugivorous birds may promote seed dispersal of many bird‐dispersed plant species. As forest loss and fragmentation of Chaco subtropical forests increase, understanding the pivotal role of mobile links exerted by avian seed dispersers is vital to maintaining and conserving this unique ecosystem.