Browsing by Author "Lobo, Jorge M."
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- Arthropod assemblage homogenization in oceanic islands: The role of indigenous and exotic species under landscape disturbancePublication . Florencio, Margarita; Cardoso, Pedro; Lobo, Jorge M.; Azevedo, Eduardo B.; Borges, Paulo A. V.Human landscape disturbance can drive the degradation of natural environments, thereby contributing to indigenous (endemic and native nonendemic) species extinctions, facilitating the establishment of exotic species and ultimately resulting in more similar species compositions over time and space. We assessed whether similarities in epigean arthropod assemblages differ between indigenous and exotic species in an oceanic archipelago, and we also examined whether such assemblage similarities depend on the most dominant species, the island, the type of habitat, the degree of landscape disturbance or local environmental variables.
- Assessing the completeness of bryophyte inventories: an oceanic island as a case study (Terceira, Azorean archipelago)Publication . Aranda, Silvia C.; Gabriel, Rosalina; Borges, Paulo A. V.; Lobo, Jorge M.How useful, complete or unbiased are comprehensive databases in order to provide reliable estimations of diversity? Using compiled data from bryophytes in Terceira Island (Azores), we specifically aim (1) to describe the register of species over time, (2) to assess the inventory completeness, i.e., the ratio between the observed and the maximum expected species, and (3) to locate the most promising areas for further surveys. First, each new recorded species was plotted against its collecting year, using the number of database-records as a surrogate of survey effort, to get the accumulation curves. These curves were then extrapolated to obtain the theoretical number of existing species according to Clench and exponential models. Spatial and habitat characteristics of the recorded taxa were also explored. Our results show an increasing trend in the rate of recorded species (c. five species per year), as well as a maximum of around a third of the theoretically “real” number of expected species that could yet remain unknown. Nevertheless, predictions of species richness were highly variable depending on the fitting curve used. Survey effort was similar between liverworts and mosses, as were inventory completeness values, but the rate of new recorded species was higher for mosses. Although bryologists visited preferably native habitats, we show that new species citations may also be found in modified habitats (e.g., exotic forests and semi-natural grasslands). We conclude that the analysis of extensive databases is a useful tool in revealing the recording and taxonomic gaps, further showing that bryophyte inventories could still be incomplete in Terceira Island. A strategy on how to improve species’ collections in remote areas is suggested, hoping to contribute to all-inclusive biodiversity studies in the Azores and elsewhere.
- Coefficient shifts in geographical ecology: an empirical evaluation of spatial and non-spatial regressionPublication . Bini, L. Mauricio; Diniz-Filho, J. Alexandre F.; Rangel, Thiago F. L. V. B.; Akre, Thomas S. B.; Albaladejo, Rafael G.; Albuquerque, Fabio S.; Aparicio, Abelardo; Araújo, Miguel B.; Baselga, Andrés; Beck, Jan; Bellocq, M. Isabel; Böhning-Gaese, Katrin; Borges, Paulo A. V.; Castro-Parga, Isabel; Chey, Vun Khen; Chown, Steven L.; Marco, Paulo de Jr; Dobkin, David S.; Ferrer-Castán, Dolores; Field, Richard; Filloy, Julieta; Fleishman, Erica; Gómez, Jose F.; Hortal, Joaquín; Iverson, John B.; Kerr, Jeremy T.; Kissling, W. Daniel; Kitching, Ian J.; León-Cortés, Jorge L.; Lobo, Jorge M.; Montoya, Daniel; Morales-Castilla, Ignacio; Moreno, Juan C.; Oberdorff, Thierry; Olalla-Tárraga, Miguel Á.; Pausas, Juli G.; Qian, Hong; Rahbek, Carsten; Rodríguez, Miguel Á.; Rueda, Marta; Ruggiero, Adriana; Sackmann, Paula; Sanders, Nathan J.; Terribile, Levi Carina; Vetaas, Ole R.; Hawkins, Bradford A.A major focus of geographical ecology and macro ecology is to understand the causes of spatially structured ecological patterns. However, achieving this understanding can be complicated when using multiple regressions, because the relative importance of explanatory variables, as measured by regression coefficients, can shift depending on whether spatially explicit or non-spatial modelling is used. However, the extent to which coefficients may shift and why shifts occur are unclear. Here, we analyze the relationship between environmental predictors and the geographical distribution of species richness, body size, range size and abundance in 97 multi-factorial data sets. Our goal was to compare standardized partial regression coefficients of non-spatial ordinary least squares regressions (i.e. models fitted using ordinary least squares without taking autocorrelation into account; “OLS models” hereafter) and eight spatial methods to evaluate the frequency of coefficient shifts and identify characteristics of data that might predict when shifts are likely. We generated three metrics of coefficient shifts and eight characteristics of the data sets as predictors of shifts. Typical of ecological data, spatial autocorrelation in the residuals of OLS models was found in most data sets. The spatial models varied in the extent to which they minimized residual spatial autocorrelation. Patterns of coefficient shifts also varied among methods and datasets, although the magnitudes of shifts tended to be small in all cases. We were unable to identify strong predictors of shifts, including the levels of autocorrelation in either explanatory variables or model residuals. Thus, changes in coefficients between spatial and non-spatial methods depend on the method used and are largely idiosyncratic, making it difficult to predict when or why shifts occur. We conclude that the ecological importance of regression coefficients cannot be evaluated with confidence irrespective of whether spatially explicit modelling is used or not. Researchers may have little choice but to be more explicit about the uncertainty of models and more cautious in their interpretation.
- The colonisation of exotic species does not have to trigger faunal homogenisation : lessons from the assembly patterns of arthropods on oceanic islandsPublication . Florencio, Margarita; Lobo, Jorge M.; Cardoso, Pedro; Almeida-Neto, Mário; Borges, Paulo A. V.Human-caused disturbances can lead to the extinction of indigenous (endemic and native) species, while facilitating and increasing the colonisation of exotic species; this increase can, in turn, promote the similarity of species compositions between sites if human-disturbed sites are consistently invaded by a regionally species-poor pool of exotic species. In this study, we analysed the extent to which epigean arthropod assemblages of four islands of the Azorean archipelago are characterised by nestedness according to a habitat-altered gradient. The degree of nestedness represents the extent to which less ubiquitous species occur in subsets of sites occupied by the more widespread species, resulting in an ordered loss/gain of species across environmental or ecological gradients. A predictable loss of species across communities while maintaining others may lead to more similar communities (i.e. lower beta-diversity). In contrast, anti-nestedness occurs when different species tend to occupy distinct sites, thus characterising a replacement of species across such gradients. Our results showed that an increase in exotic species does not promote assemblage homogenisation at the habitat level. On the contrary, exotic species were revealed as habitat specialists that constitute new and well-differentiated assemblages, even increasing the species compositional heterogeneity within human-altered landscapes. Therefore, contrary to expectations, our results show that both indigenous and exotic species established idiosyncratic assemblages within habitats and islands. We suggest that both the historical extinction of indigenous species in disturbed habitats and the habitat-specialised character of some exotic invasions have contributed to the construction of current assemblages.
- Designing a survey protocol to overcome the Wallacean shortfall: a working guide using bryophyte distribution data on Terceira Island (Azores)Publication . Aranda, Silvia C.; Gabriel, Rosalina; Borges, Paulo A. V.; Azevedo, Eduardo B.; Lobo, Jorge M.The increasing availability of open access data on species occurrences is leading researchers to generate more hypotheses about patterns of species distributions. However, when all of this information is mapped onto a particular geographical scale, gaps usually appear due to lack of knowledge and sampling spatial bias (the so-called Wallacean shortfall). To overcome these problems as efficiently as possible, field surveys should be designed after distinguishing well-surveyed places from those with incomplete inventories in order to carry out the extra survey effort in those areas not represented environmentally and spatially by the well-surveyed places. This procedure requires (1) gathering, cleaning and standardizing data; (2) selecting environmental variables that are important for the group considered according to field experience and the literature; and (3) making statistical decisions about the number and location of areas that should be surveyed according to the available resources. Here, we summarize most concepts and procedures devoted to the evaluation of biodiversity data, offering some general recommendations on how to use them for optimizing new survey designs. As a practical guide for potential users, we provide an example describing its application to a comprehensive database on bryophyte distribution on Terceira Island (Azores, Portugal). More than 8,000 bryophyte records were gathered, but (i) less than half of the island area has been surveyed at least once and (ii) less than 1% of these have reliable inventories (placed on the few remnants of laurel forests that have been traditionally better surveyed). Nevertheless, surveying just 15 additional localities evenly distributed across the major environmental regions and habitats on Terceira Island seems to represent the existing environmental diversity. We believe that the survey protocol presented here for bryophytes of Terceira Island could be flexibly applied to other taxa or areas.
- Functional traits of indigenous and exotic ground-dwelling arthropods show contrasting responses to land-use changes in an oceanic island, Terceira, AzoresPublication . Rigal, François; Cardoso, Pedro; Lobo, Jorge M.; Triantis, Kostas A.; Whittaker, Robert J.; Amorim, Isabel R.; Borges, Paulo A. V.AIM: Land-use change typically goes hand in hand with the introduction of exotic species, which mingle with indigenous species to form novel assemblages. Here, we compare the functional structure of indigenous and exotic elements of ground-dwelling arthropod assemblages across four land-uses of varying management intensity. LOCATION: Terceira Island (Azores, North Atlantic). METHODS: We used pitfall traps to sample arthropods in 36 sites across the four land-uses and collated traits related to dispersal ability, body size and resource use. For both indigenous and exotic species, we examined the impact of land-uses on trait diversity and tested for the existence of non-random assembly processes using null models. We analysed differences in trait composition among land-uses for both indigenous and exotic species with multivariate analyses. We used point–biserial correlations to identity traits significantly correlated with specific land-uses for each element. RESULTS: We recorded 86 indigenous and 116 exotic arthropod species. Under high-intensity land-use, both indigenous and exotic elements showed significant trait clustering. Trait composition strongly shifted across land-uses, with indigenous and exotic species being functionally dissimilar in all land-uses. Large-bodied herbivores dominated exotic elements in low-intensity land-uses, while small-bodied spiders dominated exotic elements in high-intensity land-uses. In contrast, with increasing land-use intensity, indigenous species changed from functionally diverse to being dominated by piercing and cutting herbivores. Main conclusions: Our study revealed two main findings: first, in high-intensity land-uses, trait clustering characterized both indigenous and exotic elements; second, exotic species differed in their functional profile from indigenous species in all land-use types. Overall, our results provide new insights into the functional role of exotic species in a land-use context, suggesting that, in agricultural landscape, exotic species may contribute positively to the maintenance of some ecosystem functions.
- Geographical, temporal and environmental determinants of bryophyte species richness in the Macaronesian IslandsPublication . Aranda, Silvia C.; Gabriel, Rosalina; Borges, Paulo A. V.; Santos, Ana M. C.; Azevedo, Eduardo B.; Patiño, Jairo; Hortal, Joaquín; Lobo, Jorge M.Species richness on oceanic islands has been related to a series of ecological factors including island size and isolation (i.e. the Equilibrium Model of Island Biogeography, EMIB), habitat diversity, climate (i.e., temperature and precipitation) and more recently island ontogeny (i.e. the General Dynamic Model of oceanic island biogeography, GDM). Here we evaluate the relationship of these factors with the diversity of bryophytes in the Macaronesian region (Azores, Madeira, Canary Islands and Cape Verde). The predictive power of EMIB, habitat diversity, climate and the GDM on total bryophyte richness, as well as moss and liverwort richness (the two dominant bryophyte groups), was evaluated through ordinary least squares regressions. After choosing the best subset of variables using inference statistics, we used partial regression analyses to identify the independent and shared effects of each model. The variables included within each model were similar for mosses and liverworts, with orographic mist layer being one of the most important predictors of richness. Models combining climate with either the GDM or habitat diversity explained most of richness variation (up to 91%). There was a high portion of shared variance between all pairwise combinations of factors in mosses, while in liverworts around half of the variability in species richness was accounted for exclusively by climate. Our results suggest that the effects of climate and habitat are strong and prevalent in this region, while geographical factors have limited influence on Macaronesian bryophyte diversity. Although climate is of great importance for liverwort richness, in mosses its effect is similar to or, at least, indiscernible from the effect of habitat diversity and, strikingly, the effect of island ontogeny. These results indicate that for highly vagile taxa on oceanic islands, the dispersal process may be less important for successful colonization than the availability of suitable ecological conditions during the establishment phase.
- How do different dispersal modes shape the species-area relationship? Evidence for between-group coherence in the Macaronesian floraPublication . Aranda, Silvia C.; Gabriel, Rosalina; Borges, Paulo A. V.; Santos, Ana M. C.; Hortal, Joaquín; Baselga, Andrés; Lobo, Jorge M.AIM: We explore the island species–area relationships (ISARs) of several plant groups differing in dispersal ability. We examine whether: (i) the ISAR slope is higher for less dispersive groups (diminishing from not-wind-dispersed seed plants to wind-dispersed seed plants, pteridophytes and bryophytes); and (ii) the regional richness is higher than that predicted by the ISAR of its constituent islands for groups with lower dispersal ability. Additionally, we relate both patterns to the compositional dissimilarity (beta diversity) between islands. LOCATION: The Macaronesian archipelagos of the Azores, Madeira and Canary Islands. METHODS: ISARs were estimated using the conventional power model. Differences in slopes among taxa were analysed through ANCOVA tests. We assessed the deviation of the total richness of the Macaronesian flora from that predicted by the ISAR and calculated several measures of beta diversity (turnover, nestedness-resultant dissimilarity and nestedness). Analyses were repeated after excluding the two Canarian islands of Lanzarote and Fuerteventura, which have unique climatic and geological conditions in the region. RESULTS: All ISAR models were significant except for pteridophytes (for which it was significant when excluding Lanzarote and Fuerteventura). ISAR slopes did not differ among taxa. Regional richness followed ISAR predictions for bryophytes and pteridophytes when Lanzarote and Fuerteventura were excluded, while the total number of Macaronesian seed plants (particularly not-wind-dispersed species) always fell above the ISAR. Turnover was higher in seed plants than in bryophytes and pteridophytes, and the opposite occurred with nestedness. MAIN CONCLUSIONS: Differences in dispersal ability influence the compositional dissimilarity between these islands, but not the rate of species increase with area. This may be because ISAR slopes are mostly determined by within-island processes of species accumulation, while differences in dispersal generate different between island patterns. The lack of relationship between the ISAR slope and species replacement or nestedness prevents its use as a proxy for beta diversity.
- Invasibility and species richness of island endemic arthropods: a general model of endemic vs. exotic speciesPublication . Borges, Paulo A. V.; Lobo, Jorge M.; Azevedo, Eduardo B.; Gaspar, Clara; Melo, Catarina; Nunes, Luis V.This paper has two objectives. First, we examine how a variety of biotic, abiotic and anthropogenic factors influence the endemic and introduced arthropod richness on an oceanic island. Second, we look at the relationship between the endemic and introduced arthropod richness, to ask whether areas with high levels of endemic species richness deter invasions.
- The iterative process of plant species inventorying for obtaining reliable biodiversity patternsPublication . Aranda, Silvia C.; Hespanhol, Helena; Homem, Nídia; Borges, Paulo A. V.; Lobo, Jorge M.; Gabriel, RosalinaWe require representative data of species occurrence to explain plant diversity patterns, but most of the available information is incomplete and biased. To improve our knowledge, we suggest that species inventorying should be an iterative process encompassing the following: (1) the detection of taxonomic and geographical gaps; (2) the planning of a survey design to reduce such gaps; and (3) the evaluation of field sampling results. Here, we focus on the latter phase for the bryophytes of Terceira Island (Azores) for which we have previously estimated < 1% of the area as well surveyed based on historical collections. To examine the performance of our stratified survey based on two factors (land use and environmental regions), we used rarefaction curves, ANOVA tests and bootstrap sampling. We recorded 40% of all the species known for the island and presented eight new citations. The species assemblages remained similar between historical and current inventories. Most localities had completeness values > 85%, but we always exceeded the optimal sampling effort. Land uses and environmental regions affected species diversity, but, unexpectedly, to a different degree. Our study illustrates the difficulties of planning field surveys to obtain reliable biodiversity patterns, even when prior information and standardized sampling protocols are explicitly considered.