Islands,mainland, and terrestrial fragments: How isolation shapes plant diversity

The fragmentation of natural habitats is a major threat for biodiversity. However, the impact and spatial scale of natural isolation mechanisms leading to species loss, compared to anthropogenic fragmentation, are not clear, mainly due to differences between fragments and islands, such as matrix permeability. We studied a 500 km² Mediterranean region in France, including urban habitat fragments, continuous habitat, and continental‐shelf islands. On the basis of 295 floristic relevés, we built species–area relationships to compare isolation in fragments after urbanization, with continuous habitat and continental‐shelf islands. We assumed either no dispersal, infinite dispersal, or estimated intermediate levels of habitat reachability through graph theory. Isolation mechanisms occurred in fragments but with a lower strength than in near‐shore islands, and most importantly affected perennial plants. Annual plants were less affected, probably due to their smaller size and shorter life cycle. Isolation occurred at landscape level in fragments and at patch level in islands. The amount of reachable habitat (accounting for spatial configuration) explained local species richness in both systems, but the amount of habitat (no consideration of spatial configuration) was already a good predictor. These results suggest an important role of habitat amount around fragments in mitigating the isolation effects observed in near‐shore islands, and the importance of carefully considering different functional groups.     

Zoogeography of the shorefish fauna of Clipperton Atoll

One hundred and fifteen species of fishes (14 oceanic, plus 101 shore and nearshore species) are known from Clipperton Island, a small, remote coral atoll in the tropical eastern Pacific (TEP). This fish fauna includes only 14% of the region's shallow-water species, and also is depauperate relative to the fish faunas of other isolated tropical islands. The island's isolation, small size, reduced habitat diversity, and oceanic environment contribute to this paucity of species.Fifty-two species at Clipperton can be identified as TEP; these include 37 widespread species, six species shared only with the Revillagigedo Islands [the nearest (950 km) offshore shoals], and eight endemic to Clipperton. Endemics species apparently have a mix of west and east Pacific origins. Sixty-three species are transpacific; they include three new records (of Naso surgeonfishes) that maybe vagrants recruited > 4,000 km from Oceania.Clipperton is situated at the juncture between the TEP and Oceania. Its fish fauna contains about equal numbers of TEP and transpacific species. This faunal structure reflects the relative influence of surface currents from Oceania and the TEP. Although most of Clipperton's transpacific shorefishes are widespread in eastern Oceania, the Clipperton fauna has specific affinities to the fauna of the Line Islands, which are located within the main eastbound current from Oceania. Clipperton may therefore be a major stepping stone for dispersal between Oceania and the remainder of the TEP. About 50% of the non-oceanic, tropical transpacific fishes occur there, and at least 75 % of those species apparently have resident populations at the island.     

Factors determining mammal species richness on habitat islands and isolates: habitat diversity, disturbance, species interactions and guild assembly rules

• 1 For over three decades the equilibrium theory of island biogeography has galvanized studies in ecological biogeography. Studies of oceanic islands and of natural habitat islands share some similarities to continental studies, particularly in developed regions where habitat fragmentation results from many land uses. Increasingly, remnant habitat is in the form of isolates created by the clearing and destruction of natural areas. Future evolution of a theory to predict patterns of species abundance may well come from the application of island biogeography to habitat fragments or isolates.
• 2 In this paper we consider four factors other than area and isolation that influence the number and type of mammal species coexisting in one place: habitat diversity, habitat disturbance, species interactions and guild assembly rules. In all examples our data derive from mainland habitat, fragmented to differing degrees, with different levels of isolation.
• 3 Habitat diversity is seen to be a good predictor of species richness. Increased levels of disturbance produce a relatively greater decrease in species richness on smaller than on larger isolates. Species interactions in the recolonization of highly disturbed sites, such as regenerating mined sites, is analogous to island colonization. Species replacement sequences in secondary successions indicate not just how many, but which species are included. Lastly, the complement of species established on islands, or in insular habitats, may be governed by guild assembly rules. These contributions may assist in taking a renewed theory into the new millennium.

     

Effects of habitat size and isolation on species immigration–extinction dynamics and community nestedness in a desert river system

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Variation in reef fish and invertebrate communities with level of protection from fishing across the Eastern Tropical Pacific seascape

Aim To quantify general differences in reef community structure between well‐enforced and poorly enforced marine protected areas (MPAs) and fished sites across the Eastern Tropical Pacific (ETP) regional seascape Location The Pacific continental margin and oceanic islands of Costa Rica, Panama, Colombia and Ecuador, including World Heritage sites at Galapagos, Coiba, Cocos and Malpelo Methods Densities of reef fishes, mobile and sessile invertebrates, and macroalgae were quantified using underwater visual surveys at 136 ‘no‐take’ and 54 openly fished sites associated with seven large MPAs that encompassed a range of management strategies. Spatial variation in multivariate and univariate community metrics was related to three levels of fishing pressure (high‐protection MPAs, limited‐protection MPAs, fishing zones) for both continental and oceanic reefs. Results High‐protection MPAs possessed a much greater biomass of higher carnivorous fishes, lower densities of asteroids and Eucidaris spp. urchins, and higher coral cover than limited‐protection MPAs and fished zones. These results were generally consistent with the hypothesis that overfishing of predatory fishes within the ETP has led to increased densities of habitat‐modifying macroinvertebrates, which has contributed to regional declines in coral cover. Major differences in ecological patterns were also evident between continental and oceanic biogeographic provinces. Main conclusions Fishing down the food web, with associated trophic cascades, has occurred to a greater extent along the continental coast than off oceanic islands. Poorly enforced MPAs generate food webs more similar to those present in fished areas than in well‐protected MPAs.     

Biogeography of the Tropical Eastern Pacific: distribution and phylogeny of chaenopsid fishes

The Tropical Eastern Pacific Biogeographic Region (TEP) is delimited by steep thermal gradients to the north and south, by a wide expanse of open ocean (the East Pacific Barrier) to the west, and by the Central American land mass to the east. Four provinces within the TEP have been recognized based on the distribution of rocky shore fishes and marine invertebrates: the Cortez, Mexican, Panamic, and Galápagos Provinces. For rocky shore fishes, hypothesized barriers between these provinces are areas lacking rocky outcroppings, specifically the Central American Gap between the Panamic and Mexican Provinces, the Sinaloan Gap between the Mexican and Cortez Provinces, and the Pelagic Gap between the mainland and the Islas Galápagos. The occurrence of 33 chaenopsid fish species within these provinces, as well as other oceanic islands or archipelagos in the TEP (Isla de Malpelo, Isla del Coco, and Islas Revillagigedo) were tallied based on literature records and observations of museum specimens. Chaenopsid distributions within the TEP support these hypothesized provinces and their intervening gaps. Twenty‐one species (64% of the TEP chaenopsid fauna) are restricted to a single mainland province or one of the oceanic islands or archipelagos. Of the mainland provinces, the Cortez and Panamic exhibit similar levels of endemism (50%), but the Mexican Province has only one endemic (10%). Of the remaining chaenopsids in the Mexican Province, three are widespread, occurring in all three mainland provinces, four are shared only with the Cortez Province, and two are shared only with the Panamic Province. Within the TEP, the Pelagic Gap is the most effective (crossed by only 3 of 33 species adjacent to it), followed by the Central American Gap (crossed by 5 of 21 species), and the Sinaloan Gap (crossed by 7 of 17 species). Only one species, Chaenopsis alepidota, which is found off southern California and in the Cortez Province, crosses a barrier delimiting the TEP. Species‐level phylogenetic hypotheses for the Chaenopsidae imply exclusively allopatric speciation for these fishes in the TEP. Of the barriers delimiting the TEP, the most important in the recent evolution of chaenopsids is the Isthmian Barrier which is implicated in six speciation events. Within the TEP, the Central American Gap and Sinaloan Gap are each implicated in three speciation events, while the Pelagic Gap is implicated in three speciation events of island endemics from mainland populations and one inter‐island speciation event.     

Body size distributions in North American freshwater fish: large‐scale factors

Aim To document continental‐ and regional‐scale variation in the size distributions of freshwater fish and examine some energetic, evolutionary and biogeographic explanations for these patterns. Location North America. Methods Regional species lists, coupled with habitat and body size information, were used to document the spatial patterns. Results At the continental scale, riverine specialist fishes show a unimodal, right‐skewed, body size distribution whereas habitat generalist and lacustrine specialist species exhibit bimodal size distributions, with only a slight preponderance of small‐mode species. Most large‐mode species are migratory. Resident species, unlike migratory ones, show a latitudinal increase in mean size, but the size increase across all species is steeper because the importance of large migratory species increases with latitude. Size distributions change from right‐ to left‐skewed with increasing latitude. Maximum body size does not change with increasing family richness but minimum size declines and skewness increases, consistent with diversification of small species. Skewness does not vary with mean family body size. Main conclusions Post‐glacial recolonization by large, habitat generalist, migratory species is the main determinant of latitudinal size distribution trends. There is little support for the energetic hypothesis, but the data are consistent with a negative Cope's rule.     

Island biogeography of bats in Baja California, Mexico: patterns of bat species richness in a near-shore archipelago

Aim We studied the relationship between the size and isolation of islands and bat species richness in a near‐shore archipelago to determine whether communities of vagile mammals conform to predictions of island biogeography theory. We compared patterns of species richness in two subarchipelagos to determine whether area per se or differences in habitat diversity explain variations in bat species richness. Location Islands in the Gulf of California and adjacent coastal habitats on the Baja California peninsula in northwest Mexico. Methods Presence–absence surveys for bats were conducted on 32 islands in the Gulf of California using acoustic and mist‐net surveys. We sampled for bats in coastal habitats of four regions of the Baja peninsula to characterize the source pool of potential colonizing species. We fitted a semi‐log model of species richness and multiple linear regression and used Akaike information criterion model selection to assess the possible influence of log₁₀ area, isolation, and island group (two subarchipelagos) on the species richness of bats. We compared the species richness of bats on islands with greater vegetation densities in the southern gulf (n = 20) with that on drier islands with less vegetation in the northern gulf (n = 12) to investigate the relationship between habitat diversity and the species richness of bats. Results Twelve species of bats were detected on islands in the Gulf of California, and 15 species were detected in coastal habitats on the Baja peninsula. Bat species richness was related to both area and isolation of islands, and was higher in the southern subarchipelago, which has denser vegetation. Log₁₀ area was positively related to bat species richness, which increased by one species for every 5.4‐fold increase in island area. On average, richness declined by one species per 6.25 km increase in isolation from the Baja peninsula. Main conclusions Our results demonstrate that patterns of bat species richness in a near‐shore archipelago are consistent with patterns predicted by the equilibrium theory of island biogeography. Despite their vagility, bats may be more sensitive to moderate levels of isolation than previously expected in near‐shore archipelagos. Differences in vegetation and habitat xericity appear to be associated with richness of bat communities in this desert ecosystem. Although observed patterns of species richness were consistent with those predicted by the equilibrium theory, similar relationships between species richness and size and isolation of islands may arise from patch‐use decision making by individuals (optimal foraging strategies).     

Habitat alteration and its effects on native fishes in the upper Tennessee River system, east-central U.S.A.

The upper Tennessee River drainage, which includes portions of the States of Virginia, North Carolina, and Tennessee, supports an exceptionally diverse fish fauna. Recent reductions in abundance and geographic ranges of several freshwater fishes have promulgated the imposition of protective measures for about 115 species among the three states, with nearly half of those species occurring in the upper Tennessee River. Most protected species are darters (Percidae: Etheostomatinae) or minnows (Cyprinidae), and are typically small, benthic invertivores. Major impacts on the fish fauna have resulted from dams, introduced species, toxic spills, mining and agriculture. An important cumulative effect of these impacts is fragmentation of the watershed; nearly 40% of the riverine habitat in major tributaries is either impounded or altered by tailwater discharges. The isolation and stress imposed on tributaries of the river have caused and will continue to cause extirpations of fishes, mussels and other aquatic fauna. Numerous federal, state, and private organizations are co-operating in efforts to protect rare species and habitats, improve agricultural and coal-producing practices, and enforce regulations for industrial and municipal effluents.     

Reduced flight capability in British Virgin Island populations of a wing-dimorphic insect: the role of habitat isolation, persistence, and structure

1. The effects of habitat isolation, persistence, and host‐plant structure on the incidence of dispersal capability (per cent macroptery) in populations of the delphacid planthopper Toya venilia were examined throughout the British Virgin Islands. The host plant of this delphacid is salt grass Sporobolus virginicus, which grows either in undisturbed habitats (large expanses on intertidal salt flats and around the margins of salt ponds, or small patches of sparse vegetation on sand dunes along the shore), or in less persistent, disturbed habitats (managed lawns). 2. Both sexes of T. venilia were significantly more macropterous in disturbed habitats (77.1% in males, 12.5% in females) than in more persistent, undisturbed habitats (19.2% in males, < 1% in females). 3. Males exhibited significantly higher levels of macroptery (26.9 ± 7.6%) than did females (2.0 ± 1.7%), and per cent macroptery was positively density dependent for both sexes in field populations. 4. There was no evidence that the low incidence of female macroptery in a subset of island populations inhabiting natural habitats (1.7 ± 1.2%) was attributable to the effects of isolation on oceanic islands. The incidence of macroptery in British Virgin Island populations of T. venilia was not different from that observed in mainland delphacid species existing in habitats of similar duration. 5. Rather, the persistence of most salt grass habitats throughout the British Virgin Islands best explains the evolution of flight reduction in females of this island‐inhabiting delphacid. 6. Males were significantly more macropterous in populations occupying dune vegetation (37.6 ± 9.8%) than in populations occupying salt flat–pond margin habitats (7.6 ± 5.6%). By contrast, females exhibited low levels of macroptery in both dune (0%) and salt flat–pond margin (< 1%) habitats. Variation in salt‐grass structure probably underlies this habitat‐related difference in macroptery because flight‐capable males of planthoppers are better able to locate females in the sparse‐structured grass growing on dunes. This habitat‐related difference in male macroptery accounted for the generally higher level of macroptery observed in males than in females throughout the islands. 7. The importance of habitat persistence and structure in explaining the incidence of dispersal capability in T. venilia is probably indicative of the key role these two factors play in shaping the dispersal strategies of many insects.     

Fish species diversity in sand bank habitats of a neotropical river

The fish fauna of the Cinaruco River, an intermediate sized floodplain river that forms the southern boundary of the newly established Santos Luzardo National Park in the llanos of Venezuela, was sampled in 1993-1994. Due to highly seasonal rainfall, the nutrient-poor Cinaruco undergoes dramatic changes in water level, creating a variety of seasonally available habitats for fishes. Sand bank habitats are conspicuous features in both main-channel and lentic backwater areas, and support fish assemblages that are different from adjacent rocky shore and shrubby shore habitats. Seine samples from sand bank habitats revealed high alpha diversity, dominated numerically by a few species of small Characiformes. Comparisons among and between lagoon, side-channel, and main-channel sand bank habitats showed little assemblage similarity. Overall, sand bank habitats were used by 8 orders, 21 families, and 105 species of fish, mostly of size classes less than 100 mm. Several species are currently undescribed. Elements which may contribute to high fish diversity include proximity to a diverse Amazonian fauna, seasonally dynamic habitat availability, the influence of keystone predators, and episodes of intermediate disturbance, such as seasonal release from intense biotic interactions.     

The roles of geological history and colonization abilities in genetic differentiation between mammalian populations in the Philippine archipelago

Aim To test hypotheses that: (1) late Pleistocene low sea‐level shorelines (rather than current shorelines) define patterns of genetic variation among mammals on oceanic Philippine islands; (2) species‐specific ecological attributes, especially forest fidelity and vagility, determine the extent to which common genetic patterns are exhibited among a set of species; (3) populations show reduced within‐population variation on small, isolated oceanic islands; (4) populations tend to be most highly differentiated on small, isolated islands; and (5) to assess the extent to which patterns of genetic differentiation among multiple species are determined by interactions of ecological traits and geological/geographic conditions. Location The Philippine Islands, a large group of oceanic islands in Southeast (SE) Asia with unusually high levels of endemism among mammals. Methods Starch‐gel electrophoresis of protein allozymes of six species of small fruit bats (Chiroptera, Pteropodidae) and one rodent (Rodentia, Muridae). Results Genetic distances between populations within all species are not correlated with distances between present‐day shorelines, but are positively correlated with distances between shorelines during the last Pleistocene period of low sea level; relatively little intraspecific variation was found within these ‘Pleistocene islands’. Island area and isolation of oceanic populations have only slight effects on standing genetic variation within populations, but populations on some isolated islands have heightened levels of genetic differentiation, and reduced levels of gene flow, relative to other islands. Species associated with disturbed habitat (all of which fly readily across open habitats) show more genetic variation within populations than species associated with primary rain forest (all of which avoid flying out from beneath forest canopy). Species associated with disturbed habitats, which tend to be widely distributed in SE Asia, also show higher rates of gene flow and less differentiation between populations than species associated with rain forest, which tend to be Philippine endemic species. One rain forest bat has levels of gene flow and heterozygosity similar to the forest‐living rodent in our study. Main conclusions The maximum limits of Philippine islands that were reached during Pleistocene periods of low sea level define areas of relative genetic homogeneity, whereas even narrow sea channels between adjacent but permanently isolated oceanic islands are associated with most genetic variation within the species. Moreover, the distance between ‘Pleistocene islands’ is correlated with the extent of genetic distances within species. The structure of genetic variation is strongly influenced by the ecology of the species, predominantly as a result of their varying levels of vagility and ability to tolerate open (non‐forested) habitat. Readily available information on ecology (habitat association and vagility) and geological circumstances (presence or absence of Pleistocene land‐bridges between islands, and distance between oceanic islands during periods of low sea level) are combined to produce a simple predictive model of likely patterns of genetic differentiation (and hence speciation) among these mammals, and probably among other organisms, in oceanic archipelagos.     

Utilizing a multifaceted approach to assess the current distribution and conservation status of an uncommon species: the golden mouse (Ochrotomys nuttalli) in Florida

Aim

Our goal was to assess the conservation status of the understudied and naturally uncommon habitat specialist, the golden mouse (Ochrotomys nuttalli), at the edge of its range where its historically fragmented habitat has been subjected to severe loss.

Location

Peninsular Florida, north of approximately 27° latitude, USA.

Methods

We used data gathered from museum collections, regional biologists, geographic information systems (GIS) layers, field surveys and DNA sequencing to determine the habitats that best explain the distribution of the species, examine changes in the geographic extent of both the species and its habitats, and compare genetic differentiation between populations occupying disjunct regions. The results from these multiple analyses were combined to assess the conservation status of the species.

Results

Golden mouse occurrence records align well with the distribution of hardwood habitats in Florida. These habitats occur naturally as ‘islands’, but have become increasingly fragmented by anthropogenic land use. Despite habitat loss, the location of the southern range periphery has remained relatively unchanged in location over the past century. Genetic analysis reveals a history of limited dispersal of females among habitat ‘islands’ that likely predates anthropogenic landscape fragmentation. This pattern suggests that isolated populations that are extirpated will have little to no chance of successful recolonization.

Main conclusions

The combined results from multiple analyses produced a more complete picture of the threats faced by this previously data‐deficient species than any single analysis would have. Although the species' southern range limit cannot be shown to have retracted in the face of human expansion, habitat fragmentation clearly has put the species at increased risk. Conservation and management of hardwood habitats are critical to the persistence of the golden mouse at the edge of its range.     

Habitat filtering not dispersal limitation shapes oceanic island floras: species assembly of the Galápagos archipelago

Remote locations, such as oceanic islands, typically harbour relatively few species, some of which go on to generate endemic radiations. Species colonising these locations tend to be a non‐random subset from source communities, which is thought to reflect dispersal limitation. However, non‐random colonisation could also result from habitat filtering, whereby only a few continental species can become established. We evaluate the imprints of these processes on the Galápagos flora by analysing a comprehensive regional phylogeny for ~ 39 000 species alongside information on dispersal strategies and climatic suitability. We found that habitat filtering was more important than dispersal limitation in determining species composition. This finding may help explain why adaptive radiation is common on oceanic archipelagoes – because colonising species can be relatively poor dispersers with specific niche requirements. We suggest that the standard assumption that plant communities in remote locations are primarily shaped by dispersal limitation deserves reconsideration.     

Explanations for bird species range size: ecological correlates and phylogenetic effects in the Canary Islands

Aim To explore the determinants of island occupancy of 48 terrestrial bird species in an oceanic archipelago, accounting for ecological components while controlling for phylogenetic effects. Location The seven main islands of the Canary archipelago. Methods We obtained field data on population density, habitat breadth and landscape distribution in Tenerife, Fuerteventura and La Palma, aiming to sample all available habitats and the gradient of altitudes. In total, 1715 line transects of 0.5 km were carried out during the breeding season. We also reviewed the literature for data on occupancy, the distance between the Canary Islands and the nearest distribution border on the mainland, body size and endemicity of the 48 terrestrial bird species studied. Phylogenetic eigenvector regression was used to quantify (and to control for) the amount of phylogenetic signal. Results The two measurements of occupancy (number of occupied islands or 10 × 10 km UTM squares) were tightly correlated and produced very similar results. The occupancy of the terrestrial birds of the Canary Islands during the breeding season had a very low phylogenetic effect. Species with broader habitat breadth, stronger preferences for urban environments, smaller body size, and a lower degree of endemicity had a broader geographical distribution in the archipelago, occupying a larger number of islands and 10 × 10 UTM squares. Main conclusions The habitat‐generalist species with a tolerance for novel urban environments tend to be present on more islands and to occupy a greater area, whereas large‐sized species that are genetically differentiated within the islands are less widespread. Therefore, some properties of the ranges of these species are explicable from basic biological features. A positive relationship of range size with local abundance, previously shown in continental studies, was not found, probably because it relies on free dispersal on continuous landmasses, which may not be applicable on oceanic islands.     

Global distribution of Risso's dolphin Grampus griseus: a review and critical evaluation

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Hydrologic Connectivity Affects Fish Assemblage Structure,Diversity, and Ecological Traits in the Unregulated Gambia River,West Africa

The Gambia River of West Africa is a large unobstructed river, characterized by a natural flow regime and lateral connectivity across its floodplain. Construction of a major dam, however, is planned. We compared patterns of fish diversity, habitat use, assemblage structure, and the distribution of trophic position and body morphology in riverine and floodplain habitats in Niokolo Koba National Park, located downstream of the planned dam site. A total of 49 fish species were captured, revealing a lognormal distribution as expected for species‐rich assemblages. Fish species exhibited a range of habitat use patterns, from generalist to highly habitat‐specific, and appeared to migrate laterally among habitats between seasons. Species richness was homogenous among habitats in the wet season yet appeared to increase with isolation from the main river in the dry season. Fish assemblage structure was best explained by the interaction between habitat type and season, underlining the importance of the natural flow regime and lateral connectivity among floodplain habitats. The abundance of fishes having elongate bodies increased with isolation from the main channel in the wet season only. The distribution of fishes having compressed cross‐sectional morphology decreased with isolation from the main channel in the dry season only. These patterns of trait distribution support the conclusion that variation in hydrologic connectivity structures the fish assemblage. Our results suggest that altered flow regimes and loss of floodplain habitats after damming could lead to both decreased taxonomic and functional diversity of the fish assemblage.     

Seashore in the mountain: limestone‐associated land snail fauna on the oceanic Hahajima Island (Ogasawara Islands,Western Pacific)

Because land snails inhabiting the seashore are most likely to be carried by ocean currents or by attaching to seabirds, land snail fauna on oceanic islands include species derived from the mainland ancestors inhabiting the seashore. If habitat use of the island descendants is constrained by the ecology of the mainland ancestor, the island species that moved from the coastal habitat to the inland habitat may still be restricted to relatively exposed microhabitats with high pH, calcium carbonate‐rich substrates, and poor litter cover. We tested this hypothesis by investigating the association between environmental conditions and species diversity of seashore‐derived species of the endemic land snails on the oceanic Hahajima Island (Ogasawara Islands). Seashore‐derived species showed higher species richness on limestone outcrops than non‐limestone areas, whereas the other species showed no significant increase in species richness in limestone outcrops. There was a higher proportion of seashore‐derived species on the limestone ridges than on the soil of dolines, even in the limestone area. Accordingly, the species derived from the seashore of the mainland are restricted to microhabitats with poor vegetation cover, poor litter cover, high pH, and calcium carbonate‐rich substrates, which supports the hypothesis that the inland species on an island derived from the mainland seashore still prefer environments similar to the seashore. In addition, the seashore‐derived species on the limestone outcrop include cave‐dwellers lacking functional eyes. This suggests that the probability of colonizing a cave environment is restricted to seashore‐derived species. The findings obtained in the present study suggest that habitat use of the ancestral lineages can constrain habitat use of the descendants, even in the oceanic islands with depauperate fauna. This bias in the species composition on the limestone outcrop constrains lineages that can colonize and adapt to the inside of caves, and therefore, habitat use of the ancestral lineages affects the ability of descendant lineages to colonize novel habitats. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 102 , 686–693.     

Island biogeography of temporary wetland carabid beetle communities

Aim The study tests if island biogeography is applicable to invertebrate communities of habitat islands in the agricultural landscape that are not fragments of formerly larger habitats. Location Thirty temporary wetlands in the agricultural landscape of northeast Germany. Methods The composition and species richness of carabid beetle communities was analysed. Habitat area, isolation, the density of temporary wetlands in the landscape, land‐use intensity and the maximum duration of flooding were recorded as independent variables. Overall species richness and wetland species richness were studied in independent regression analyses. The community composition was analysed by means of a Canonical Correspondence Analysis (CCA). A partial CCA was used to analyse the effect of the distance to the edge of the field after removing impacts of other independent variables. Results The area of the habitats and various measures of isolation (mean distances = 81–240 m) did not influence species richness or wetland species richness. The community composition was mainly determined by the land‐use intensity, habitat area did not have significant effects, and the distance to the edge of the field was the only effective isolation parameter. Short‐winged species were more often affected by the distance to the edge of the field than full‐winged species. Main conclusion There is evidence that the distances between the wetlands do not provide an effective barrier to the species dispersal and, therefore, metapopulation structures including subpopulations of multiple temporary wetlands might counteract local area effects on subpopulations. Short‐winged species, however, might be more affected by isolation than full‐winged species. As carabid beetle community structure in most early successional habitats is similar, these results may be representative of many agricultural landscape habitats. Nature conservancy concepts that aim to increase habitat area and habitat connectivity have successfully been applied to fragmented late‐successional habitats. The present study indicates that such concepts do not necessarily result in higher diversity or larger populations in early successional habitats.