Claudia Baider

A spatial model of tree α-diversity and tree density for the Amazon

Large-scale patterns of Amazonian biodiversity have until now been obscured by a sparse and scattered inventory record. Here we present the first comprehensive spatial model of tree α-diversity and tree density in Amazonian rainforests, based on the largest-yet compilation of forest inventories and bolstered by a spatial interpolation technique that allows us to estimate diversity and density in areas that have never been inventoried. These data were then compared to continent-wide patterns of rainfall seasonality. We find that dry season length, while only weakly correlated with average tree α-diversity, is a strong predictor of tree density and of maximum tree α-diversity. The most diverse forests for any given DSL are concentrated in a narrow latitudinal band just south of the equator, while the least diverse forests for any given DSL are found in the Guayana Shield and Amazonian Bolivia. Denser forests are more diverse than sparser forests, even when we used a measure of diversity that corrects for sample size. We propose that rainfall seasonality regulates tree α-diversity and tree density by affecting shade tolerance and subsequently the number of different functional types of trees that can persist in an area.

The soil seed bank during Atlantic Forest regeneration in Southeast Brazil

A survey was conducted to determine the density and species composition of viable seeds buried in four stands of a tropical montane forest at Parque Estadual Intervales, Brazil. The objective was to understand: (1) how numbers and composition of the soil seed bank change as the forest regrows, and (2) how such changes affect the species available for regeneration if forests of different ages are cut down. In each forest stand (5, 18, 27-yr-old and a mature forest), 57 soil samples were collected (0-2.5 and 2.5-5 cm deep). Viable seed density of herbaceous species ranged between 11,003 seeds. m-2 (5-yr-old vegetation) and 482 (mature forest), and between 25 (5-yr-old vegetation) and 389 seeds. m-2 (mature forest) for woody plant species in the 0-5 cm soil layer, suggesting a decrease in seed stocks in the course of forest regeneration. Seeds buried in the 0-2.5 cm soil layer represented between 56.9% and 67.4% of all viable seeds. Most of the viable seeds belonged to weeds of Asteraceae, Poaceae, Malvaceae and Solanaceae. The results provide evidence that, in forests of different ages, the soil does not store seeds of the same key ecological groups involved in the regeneration of Atlantic forest. Allochthonous seeds from remaining patches of forest, as well as their vertebrate dispersers, are needed for forest regeneration since the soil seed bank does not store large seeds of shade-tolerant species.

O Banco de sementes de um trecho de uma floresta Atlântica montana (São Paulo - Brasil)

Soil seed bank of tropical forests is involved in the establishment of ecological groups and in woody species richness restoration during forest regeneration, after natural or antropic disturbances. In order to analyze the seed bank composition in a tropical montane forest, Southeastern Brazil, 57 soil samples were collected, inside a 2-hectare forest plot, representing 28,500 cm3 of collected soil. Along 17 months, 497 seeds germinated, 65% between 0 and 2.5 cm depth. They represented a density of 872 seeds/m2. The seed bank analyzed is characterized as having two components: one composed by 66 herbaceous taxa, belonging to families with high richness of pioneer species; and another composed by 19 pioneer shrub and tree species, most of them with diaspores shorter than 1 mm length. The results found in the study site suggest that in the Atlantic montane forest soil seed bank can be important for the establishment of woody species, which form ecological groups involved in forest regeneration, following slash-and-burn. After treefall gaps, seed bank is probably responsible for the establishment of Melastomataceae species, the richest and more abundant group of pioneer species sampled in gaps.

Control of invasive alien weeds averts imminent plant extinction

Invasive alien species constitute a major threat to biodiversity and cases of extinction caused by invasive alien animals are abundant. However, while invasive alien plants also harm native biota there exists a lack of cases demonstrating their ability to cause extinction of native plant species. Different alien species (vertebrates, invertebrates, pathogens etc.) commonly deliver different simultaneous impacts like predation, disease or competition. In such situations, assessing the contribution of plant invasion in causing decline of a given plant population in its natural habitat can be difficult, yet is desirable to avoid or minimize wastage of managers’ resources. Using native angiosperms in lowland wet forests of Mauritius, we first compared native seedling diversity in forest areas that have been weeded of invasive alien plants about a decade previously, with adjacent similar but non-weeded areas. Then, using the weeded area, we compared results of native plant surveys carried out around the time that invasive alien plants were controlled, with the same community about a decade latter. Species richness and abundance of seedlings were higher in the weeded areas compared to the adjacent non weeded forest. We also found that several species that were presumed extinct or critically threatened with extinction had recovered dramatically as a consequence of the sole removal of invasive alien plants. This shows that the threat posed by invasive alien plants can be overwhelmingly important in driving native plant population declines in tropical forests and that imminent plant extinctions can be averted by timely control of alien plants.

Molecular characterization of trophic ecology within an island radiation of insect herbivores (Curculionidae: Entiminae: Cratopus)

The phytophagous beetle family Curculionidae is the most species‐rich insect family known, with much of this diversity having been attributed to both co‐evolution with food plants and host shifts at key points within the early evolutionary history of the group. Less well understood is the extent to which patterns of host use vary within or among related species, largely because of the technical difficulties associated with quantifying this. Here we develop a recently characterized molecular approach to quantify diet within and between two closely related species of weevil occurring primarily within dry forests on the island of Mauritius. Our aim is to quantify dietary variation across populations and assess adaptive and nonadaptive explanations for this and to characterize the nature of a trophic shift within an ecologically distinct population within one of the species. We find that our study species are polyphagous, consuming a much wider range of plants than would be suggested by the literature. Our data suggest that local diet variation is largely explained by food availability, and locally specialist populations consume food plants that are not phylogenetically novel, but do appear to represent a novel preference. Our results demonstrate the power of molecular methods to unambiguously quantify dietary variation across populations of insect herbivores, providing a valuable approach to understanding trophic interactions within and among local plant and insect herbivore communities.

Invasive Alien Plants Elicit Reduced Production of Flowers and Fruits in Various Native Forest Species on the Tropical Island of Mauritius (Mascarenes, Indian Ocean)

Biological invasions constitute a major threat to biodiversity. However, while the impact of invasive alien animals on native biota is often unambiguous, the impacts of invasive alien plants (IAP) appear to be considerably less severe and, at times, more debatable. Invasion by alien plants co-occur with other drivers of habitat change such that assessing impacts of IAP independently of these other factors may be difficult. Generalisations can be misleading, because studies reveal different responses of native plants to the presence of IAP. Therefore, there is a need to understand general trends and exceptions within a particular habitat. In the island of Mauritius, mechanical control of invasive alien plants has been implemented for decades in lowland wet forests. Weeded and non-weeded areas are very similar in all aspects, except for the control of IAP, providing an opportunity to study how IAP are affecting native plants. We monitored the reproductive output of 20-40 individuals each, of nine selected native species from different forest strata, in both weeded and adjacent non-weeded areas in a lowlan d wet forest, through direct count/estimation of the number of flower buds, flowers and fruits. Flower bud, flower and fruit production were greater in the weeded area. These results are consistent with previous findings that noted greater regeneration of native trees in these areas. This study also provides clues to reported decline of shade tolerant understory vegetation in alien invaded forest and further stresses the importance of removing alien plants to restore biodiversity and function and achieve conservation success.

Syzygiumpyneei (Myrtaceae), a new critically endangered endemic species from Mauritius.

Abstract A new species of Syzygium Gaertn. (Myrtaceae), Syzygium pyneei Byng, V. Florens & Baider, is described from Mondrain Reserve on the island of Mauritius. This species is endemic to the island and differs from any other species by its combination of cauliflory, relatively large flowers, light green to cream hypanthium, light pink stamens, short thick petioles, coriaceous leaves and round, cuneate or sub-cordate to cordate leaf bases. Syzygium pyneei Byng, V. Florens & Baider is known from only two individuals from the type locality and merits the conservation status of Critically Endangered (CR C2a(i,ii); D).

Threats to Paradise? Plant Invasions in Protected Areas of the Western Indian Ocean Islands

The islands of the Western Indian Ocean are well known for their unique biodiversity. However, much of the native habitat has been destroyed and the remainder is threatened by invasive alien species. In this review we assessed the different protected area systems, synthesised the history of invasive alien plants and actions against them, and compared contrasting approaches in habitat management across the different island groups. Of the total terrestrial area of the Western Indian Ocean Islands, a third is under formal protection (defined as all six IUCN categories of protected areas), with the proportion of protected areas and conservation status differing substantially between the islands. The awareness of the problems related to protected areas and specific invasive alien plant control actions, and which are supported by official government strategic documents, are further developed in Mauritius-Rodrigues, La Reunion, and Seychelles, but are still to be developed for the Comoros archipelago. We discuss the different approaches to management across the islands, the varying habitat types, fragmentation and degree of invasion. Invaded habitats are being managed by a range of approaches, including restoration, re-creation or inclusion as a novel ecosystem. We conclude by suggesting improvements in the protected area system in the Western Indian Ocean Islands, including priority actions that are necessary to prevent further invasion and control of invasive alien species already in the region.

On the Mauritian origin of Badula ovalifolia (Myrsinaceae), hitherto believed extinct, with complementary description

SummaryThe origin of Badula ovalifolia A. DC. (Myrsinaceae) is discussed and, on the evidence of recently collected specimens, we conclude that it is endemic to Mauritius and not to Reunion as previously recorded. The first description of the whole tree, fruit and seed and habitat and ecology are given. Conservation status is assessed using the IUCN Red List Criteria with suggestions for a species recovery programme.

A review of the dodo and its ecosystem: insights from a vertebrate concentration Lagerstätte in Mauritius

ABSTRACT The dodo Raphus cucullatus Linnaeus, 1758, an extinct and flightless, giant pigeon endemic to Mauritius, has fascinated people since its discovery, yet has remained surprisingly poorly known. Until the mid-19th century, almost all that was known about the dodo was based on illustrations and written accounts by 17th century mariners, often of questionable accuracy. Furthermore, only a few fragmentary remains of dodos collected prior to the birds extinction exist. Our understanding of the dodos anatomy was substantially enhanced by the discovery in 1865 of subfossil bones in a marsh called the Mare aux Songes, situated in southeastern Mauritius. However, no contextual information was recorded during early excavation efforts, and the majority of excavated material comprised larger dodo bones, almost all of which were unassociated. Here we present a modern interdisciplinary analysis of the Mare aux Songes, a 4200-year-old multitaxic vertebrate concentration Lagerstätte. Our analysis of the deposits at this site provides the first detailed overview of the ecosystem inhabited by the dodo. The interplay of climatic and geological conditions led to the exceptional preservation of the animal and associated plant remains at the Mare aux Songes and provides a window into the past ecosystem of Mauritius. This interdisciplinary research approach provides an ecological framework for the dodo, complementing insights on its anatomy derived from the only associated dodo skeletons known, both of which were collected by Etienne Thirioux and are the primary subject of this memoir. Citation for this article: Rijsdijk, K. F., J. P. Hume, P. G. B. de Louw, H. J. M. Meijer, A. Janoo, E. J. de Boer, L. Steel, J. de Vos, L. G. van der Sluis, H. Hooghiemstra, F. B. V. Florens, C. Baider, T. J. J. Vernimmen, P. Baas, A. H. van Heteren, V. Rupear, G. Beebeejaun, A. Grihault, J. van der Plicht, M. Besselink, J. K. Lubeek, M. Jansen, S. J. Kluiving, H. Hollund, B. Shapiro, M. Collins, M. Buckley, R. M. Jayasena, N. Porch, R. Floore, F. Bunnik, A. Biedlingmaier, J. Leavitt, G. Monfette, A. Kimelblatt, A. Randall, P. Floore, and L. P. A. M. Claessens. 2015. A review of the dodo and its ecosystem: insights from a vertebrate concentration Lagerstätte in Mauritius; pp. 3–20 in L. P. A. M. Claessens, H. J. M. Meijer, J. P. Hume, and K. F. Rijsdijk (eds.), Anatomy of the Dodo (Raphus cucullatus L., 1758): An Osteological Study of the Thirioux Specimens. Society of Vertebrate Paleontology Memoir 15. Journal of Vertebrate Paleontology 35(6, Supplement).