Diversity and Distributions

Varo‐Cruz, Nuria; Bermejo, Juan A.; Calabuig, Pascual; Cejudo, Daniel; Godley, Brendan J.; López‐Jurado, Luis F.; Pikesley, Stephen K.; Witt, Matthew J.; Hawkes, Lucy A.; Roura‐Pascual, Núria

doi: 10.1111/ddi.12439pmid: N/A

The cover image, by Lucy Hawkes et al., is based on the Biodiversity Research New findings about the spatial and temporal use of the Eastern Atlantic Ocean by large juvenile loggerhead turtles, DOI:10.1111/ddi.12413. Photo Credit:SECAC / Nuria Varo Cruz.

Brito, José C.; Tarroso, Pedro; Vale, Cândida G.; Martínez‐Freiría, Fernando; Boratyński, Zbyszek; Campos, João C.; Ferreira, Sónia; Godinho, Raquel; Gonçalves, Duarte V.; Leite, João V.; Lima, Vanessa O.; Pereira, Paulo; Santos, Xavier; Silva, Maria J. Ferreira; Silva, Teresa L.; Velo‐Antón, Guillermo; Veríssimo, Joana; Crochet, Pierre‐André; Pleguezuelos, Juan M.; Carvalho, Sílvia B.; Bode, Michael

doi: 10.1111/ddi.12416

Drapeau, Pierre; Villard, Marc‐André; Leduc, Alain; Hannon, Susan J.; Fischer, Joern

doi: 10.1111/ddi.12407pmid: N/A

Aim In managed forest landscapes, the tolerance of species to contemporary alteration of forest cover is often assumed to reflect their resilience to natural disturbances. We tested this central tenet of ecosystem‐based management by comparing the structure of forest bird assemblages among four regions with contrasting historical natural disturbance regimes. Location Canada's boreal and northern hardwood forests. Methods Using point count data from four study regions across Canada, we first determined the relative sensitivity of individual bird species to the contemporary reduction of old forest cover at stand and ‘landscape‐context’ (1‐km radius) scales with log‐linear models. The richness of species most sensitive to loss of old forest (hereafter ‘sensitive species’) was then modelled as a function of landscape‐scale changes in old forest cover. Differences in the rate of decline in the richness of sensitive species with contemporary cover of old forest were compared among regions using ANCOVA. We then compared broken‐stick regression models with linear models to detect thresholds, if present, in this relationship in each region. Results Bird assemblages from regions with relatively infrequent natural disturbances hosted more species sensitive to contemporary reduction in old forest cover. Those species were also more abundant than in regions with frequent natural disturbances, and the rate of decline in their richness with the loss of old forest was steeper in regions with infrequent natural disturbances than in those where they were frequent. However, we did not detect thresholds in this rate of decline in any study region. Main conclusions Our findings are consistent with the contention that historical natural disturbance regimes shape the response of biota to contemporary landscape alterations through evolutionary adaptation. We argue that forest management conducted within the natural range of variability in stand and landscape structure specific to a region is likely to be ecologically sustainable.

Filgueiras, Bruno K. C.; Tabarelli, Marcelo; Leal, Inara R.; Vaz‐de‐Mello, Fernando Z.; Peres, Carlos A.; Iannuzzi, Luciana; Andersen, Alan

doi: 10.1111/ddi.12410pmid: N/A

Aim In this study, we investigate whether anthropogenic land use and habitat fragmentation lead to a process of either homogenization (decreasing spatial replacement and increasing nestedness) or divergence (increasing spatial replacement and decreasing nestedness) of dung beetle assemblages in edge‐affected habitats. Location A fragmented landscape of the Atlantic forest of north‐east Brazil. Methods We investigate the extent to which beta diversity of dung beetle assemblages varies in edge‐affected habitats at different spatial scales (i.e. traps along an interior–exterior nonlinear gradient, within and among habitats). We compare species replacement and nestedness of dung beetle assemblages using (1) multiple dissimilarity measures accounting for compositional heterogeneity across forest (i.e. forest edges, core primary forest areas and small fragments) and matrix habitats (i.e. sugar cane plantations and pastures) and (2) distance matrices accounting for the multivariate structure of dissimilarity. Results (1) Each habitat supported a distinct dung beetle assemblage; (2) there was a strong influence of anthropogenic land use and fragmentation‐related effects on dung beetle β‐diversity, with species replacements increasing in edge‐affected and matrix habitats providing support for the divergence hypothesis at all spatial scales; (3) edge effects enhanced species replacement across assemblages; (4) dung beetle assemblages were not randomly distributed, with habitat type leading to a strongly nested pattern of species composition; and (5) both dung beetle replacement and nestedness were not correlated with geographic distance, whereby neighbouring sites were not necessarily more similar in their community composition. Main conclusions Species replacement is strongly influenced by habitat configuration and β‐diversity increases in edge‐affected habitats. Accordingly, anthropogenic land use and habitat fragmentation clearly promote community‐level taxonomic divergence in human‐modified landscapes. Landscape‐scale divergence likely results from a non‐random distribution of both forest‐dependent and disturbance‐adapted species across all habitats, which are in marked contrast in terms of suitability.

Irizarry, Julissa I.; Collazo, Jaime A.; Dinsmore, Stephen J.; Fischer, Joern

doi: 10.1111/ddi.12415pmid: N/A

Aim Avian communities in human‐modified landscapes exhibit varying patterns of local colonization and extinction rates, determinants of species occurrence. Our objective was to model these processes to identify habitat features that might enable movements and account for occupancy patterns in habitat matrices between the Guanica and Susua forest reserves. This knowledge is central to conservation design, particularly in ever changing insular landscapes. Location South‐western Puerto Rico. Methods We used a multiseason occupancy modelling approach to quantify seasonal estimates of occupancy, and colonization and extinction rates of seven resident avian species surveyed over five seasons from January 2010 to June 2011. We modelled parameters by matrix type, expressions of survey station isolation, quality, amount of forest cover and context (embedded in forest patch). Results Seasonal occupancy remained stable throughout the study for all species, consistent with seasonally constant colonization and extinction probabilities. Occupancy was mediated by matrix type, higher in reserves and forested matrix than in the urban and agricultural matrices. This pattern is in accord with the forest affinities of all but an open‐habitat specialist. Puerto Rican Spindalis (Spindalis portoricensis) exhibited high occupancy in the urban matrix, highlighting the adaptability of some insular species to novel environments. Highest colonization rates occurred when perching structures were at ≤ 500 m. Survey stations with at least three fruiting tree species and 61% forest cover exhibited lowest seasonal extinction rates. Main conclusions Our work identified habitat features that influenced seasonal probabilities of colonization and extinction in a human‐modified landscape. Conservation design decisions are better informed with increased knowledge about interpatch distances to improve matrix permeability, and habitat features that increase persistence or continued use of habitat stepping stones. A focus on dynamic processes is valuable because conservation actions directly influence colonization and extinction rates, and thus, a quantitative means to gauge their benefit.

Lascelles, B. G.; Taylor, P. R.; Miller, M. G. R.; Dias, M. P.; Oppel, S.; Torres, L.; Hedd, A.; Le Corre, M.; Phillips, R. A.; Shaffer, S. A.; Weimerskirch, H.; Small, C.; Visconti, Piero

doi: 10.1111/ddi.12411pmid: N/A

Aim Enhanced management of areas important for marine biodiversity are now obligations under a range of international treaties. Tracking data provide unparalleled information on the distribution of marine taxa, but there are no agreed guidelines that ensure these data are used consistently to identify biodiversity hotspots and inform marine management decisions. Here, we develop methods to standardize the analysis of tracking data to identify sites of conservation importance at global and regional scales. Location We applied these methods to the largest available compilation of seabird tracking data, covering 60 species, collected from 55 deployment locations ranging from the poles to the tropics. Methods Key developments include a test for pseudo‐replication to assess the independence of two groups of tracking data, an objective approach to define species‐specific smoothing parameters (h values) for kernel density estimation based on area‐restricted search behaviour, and an analysis to determine whether sites identified from tracked individuals are also representative for the wider population. Results This analysis delineated priority sites for marine conservation for 52 of the 60 species assessed. We compiled 252 data groupings and defined 1052 polygons, between them meeting Important Bird and Biodiversity Area criteria over 1500 times. Other results showed 13% of data groups were inadequate for site definition and 10% showed some level of pseudo‐replication. Between 25 and 50 trips were needed within a data group for data to be considered at least partially representative of the respective population. Main conclusions Our approach provides a consistent framework for using animal tracking data to delineate areas of global conservation importance, allowing greater integration into marine spatial planning and policy. The approaches we describe are exemplified for pelagic seabirds, but are applicable to a range of taxonomic groups. Covering 4.3% of the oceans, the sites identified would benefit from enhanced protection to better safeguard the threatened species populations they contain.

Martínez‐Freiría, Fernando; Tarroso, Pedro; Rebelo, Hugo; Brito, José C.; Thuiller, Wilfried

doi: 10.1111/ddi.12406pmid: N/A

Aim Climate change assessments are largely based on correlative species distribution models (SDMs) that are sensible to spatial biases or incompleteness of input distribution data. We tested whether changes on the species' climatic niche resulting from recent human‐induced range contractions have a significant influence on SDM predictions of future species distributions. Location Africa. Methods For this study, we selected two highly detectable species with acknowledged human‐induced range contractions, namely the African savanna elephant (Loxodonta africana) and giraffe (Giraffa camelopardalis). We used presence data until the 1970s to describe each species' historical distribution, while more recent data characterized the contemporary distribution. We compared the temporal variation between these species distributions using multivariate analyses and the combination of four different SDM algorithms to predict historical, contemporary and future distributional ranges under climate change scenarios. Results We show how range contraction differentially reduces the climatic variability associated with the species niche and has an important influence on the predictions of suitable climatic space and species vulnerability trend under climate change scenarios. Future predictions of the distribution of the elephant were mainly affected by the loss of occupied area at the margins of the historical distributions, resulting in a lesser predicted extent when using the contemporary dataset. As for the giraffe models, there were more dramatic consequences with large areas of West Africa failing to be predicted as suitable in the contemporary models, probably as a result from the loss of climatic information due to the species almost complete disappearance from that region. Main conclusions Our findings support the importance of considering historical distributional ranges of species in climate change studies in order to account for their full climatic niche and to derive more reliable predictions of future distribution. This is particularly important in species for which distributional ranges have been strongly affected by human activities.

Rouget, Mathieu; Robertson, Mark P.; Wilson, John R. U.; Hui, Cang; Essl, Franz; Renteria, Jorge L.; Richardson, David M.; Kühn, Ingolf

doi: 10.1111/ddi.12408pmid: N/A

Aim We develop a framework for quantifying invasions based on lagged trends in invasions (‘invasion debt’) with the aim of identifying appropriate metrics to quantify delayed responses at different invasion stages – from introduction to when environmental impacts occur. Location World‐wide; detailed case study in South Africa. Methods We define four components of invasion debt: the number of species not yet introduced but likely to be introduced in the future given current levels of introduction/propagule pressure; the establishment of introduced species; the potential increase in area invaded by established species (including invasive species); and the potential increase in impacts. We demonstrate the approach in terms of number of species for 21 known invasive Australian Acacia species globally and estimate three components of invasion debt for 58 Acacia species already introduced to South Africa by quantifying key invasion factors (environmental suitability, species invasion status, residence time, propagule pressure, spread rate and impacts). Results Current global patterns of invasive species richness reflect historical trends of introduction – most acacia species that will become invasive in southern Africa have already invaded, but there is a substantial establishment debt in South and North America. In South Africa, the likely consequence of invasion debt over the next 20 years was estimated at: four additional species becoming invasive with an average increase of 1075 km2 invaded area per invasive species. We estimate that this would require over US$ 500 million to clear. Main conclusions Our results indicate that invasion debt is a valuable metric for reporting on the threats attributable to biological invasions, that invasion debt must be factored into strategic plans for managing global change, and, as with other studies, they highlight the value of proactive management. Given the uncertainty associated with biological invasions, further work is required to quantify the different components of invasion debt.

Smith, Annabel L.; Blanchard, Wade; Blair, David P.; McBurney, Lachlan; Banks, Sam C.; Driscoll, Don A.; Lindenmayer, David B.; Richardson, David

doi: 10.1111/ddi.12414pmid: N/A

Aim Knowledge of how climate and fire regimes affect regeneration in foundation species is critical to the conservation of entire ecosystems. Different stages of regeneration often require different ecological conditions, but dynamic constraints on regeneration are poorly known for species that regenerate only after infrequent wildfires. Focussing on a long‐lived, foundation tree species (Eucalyptus regnans), we tested the hypothesis that the relative importance of fire regime variables (fire severity and time since previous fire) and environmental gradients on post‐fire regeneration would shift as seedlings developed. Location South‐eastern Australia. Methods Following a large (> 59,000 ha) summer wildfire in 2009, we sampled 131 sites (61 burnt) annually for four years (2009–2012), representing the range of environmental conditions in which E. regnans occurs. We analysed the effect of fire severity, time since fire and environmental variables on early regeneration processes critical for post‐fire species distributions: seedling establishment, seedling density and growth through different height stages (10 cm, 25 cm, 50 cm and 200 cm). Results The regeneration niche of E. regnans was defined by different factors at different stages of development. Initially, seedlings established prolifically on burnt sites, regardless of severity. Three years into the regeneration process, high‐severity fire became the dominant driver of seedling persistence and growth over 25 cm. Growth over 50 cm was dependent on environmental conditions relating to elevation and precipitation. Main conclusions Our results describe how fire occurrence, fire severity and environmental gradients affected seedling establishment, persistence and growth. The dynamic constraints on regeneration likely reflect temporal changes in the biotic and abiotic environment and variation in resource requirements during the early post‐fire years. Our findings will enable more accurate forecasts of species distributions to assist forest conservation in the face of global changes in climate and fire regimes.

Tayleur, Catherine M.; Devictor, Vincent; Gaüzère, Pierre; Jonzén, Niclas; Smith, Henrik G.; Lindström, Åke; Midgley, Guy

doi: 10.1111/ddi.12412pmid: N/A

Aims Climate change is known to drive both the reshuffling of whole assemblages and range shifts of individual species. Less is known about how local colonizations and extinctions of individual species contribute to changes at the community level. Our aim was to estimate the contribution of individual species to a change in community composition attributed to climate change and to relate these species‐specific contributions to species’ commonness, climatic niche characteristics and life history traits most likely to influence species sensitivity to climate change. Location Sweden. Methods Focussing on birds, we analysed changes from 1998 to 2012 in the Community Temperature Index (CTI), a measure of the average climatic niche of a community. Using a jackknife approach we assessed the contribution of individual species to the temporal trend in CTI in four different regions across Sweden, controlling for habitat distribution. We further tested whether species contribution was related to population trends and rarity to identify species most vulnerable to climate change. Results Community Temperature Index had increased over time with the greatest gains occurring in the north of the country, reflecting the larger temperature increases in this area. Changes in the regional CTI were driven both by warm‐dwelling species colonizing new sites and by extirpations of cold‐dwelling species. Furthermore, the community changes were influenced by both rare and common species. At the same time, the distribution changes of a large number of species were seemingly unaffected by climate change. Main conclusions Both range expansion and contractions contributed to the relative increase of warm‐dwelling species in Swedish bird communities. We successfully identified the climatic impacts on some of Sweden's rarest species, including cold‐dwelling species in the mountainous north. Our approach may be an efficient tool to use when characterizing the impacts of climate change on species and communities.