Martim Melo

Advances in Ecological Speciation: an integrative approach

The role of natural selection in promoting reproductive isolation has received substantial renewed interest within the last two decades. As a consequence, the study of ecological speciation has become an extremely productive research area in modern evolutionary biology. Recent innovations in sequencing technologies offer an unprecedented opportunity to study the mechanisms involved in ecological speciation. Genome scans provide significant insights but have some important limitations; efforts are needed to integrate them with other approaches to make full use of the sequencing data deluge. An international conference ‘Advances in Ecological Speciation’ organized by the University of Porto (Portugal) aimed to review current progress in ecological speciation. Using some of the examples presented at the conference, we highlight the benefits of integrating ecological and genomic data and discuss different mechanisms of parallel evolution. Finally, future avenues of research are suggested to advance our knowledge concerning the role of natural selection in the establishment of reproductive isolation during ecological speciation.

Tracing the colonization history of the Indian Ocean scops-owls (Strigiformes: Otus) with further insight into the spatio-temporal origin of the Malagasy avifauna

BackgroundThe island of Madagascar and surrounding volcanic and coralline islands are considered to form a biodiversity hotspot with large numbers of unique taxa. The origin of this endemic fauna can be explained by two different factors: vicariance or over-water-dispersal. Deciphering which factor explains the current distributional pattern of a given taxonomic group requires robust phylogenies as well as estimates of divergence times. The lineage of Indian Ocean scops-owls (Otus: Strigidae) includes six or seven species that are endemic to Madagascar and portions of the Comoros and Seychelles archipelagos; little is known about the species limits, biogeographic affinities and relationships to each other. In the present study, using DNA sequence data gathered from six loci, we examine the biogeographic history of the Indian Ocean scops-owls. We also compare the pattern and timing of colonization of the Indian Ocean islands by scops-owls with divergence times already proposed for other bird taxa.ResultsOur analyses revealed that Indian Ocean islands scops-owls do not form a monophyletic assemblage: the Seychelles Otus insularis is genetically closer to the South-East Asian endemic O. sunia than to species from the Comoros and Madagascar. The Pemba Scops-owls O. pembaensis, often considered closely related to, if not conspecific with O. rutilus of Madagascar, is instead closely related to the African mainland O. senegalensis. Relationships among the Indian Ocean taxa from the Comoros and Madagascar are unresolved, despite the analysis of over 4000 bp, suggesting a diversification burst after the initial colonization event. We also highlight one case of putative back-colonization to the Asian mainland from an island ancestor (O. sunia). Our divergence date estimates, using a Bayesian relaxed clock method, suggest that all these events occurred during the last 3.6 myr; albeit colonization of the Indian Ocean islands were not synchronous, O. pembaensis diverged from O. senegalensis about 1.7 mya while species from Madagascar and the Comoro diverged from their continental sister-group about 3.6 mya. We highlight that our estimates coincide with estimates of diversification from other bird lineages.ConclusionOur analyses revealed the occurrence of multiple synchronous colonization events of the Indian Ocean islands by scops-owls, at a time when faunistic exchanges involving Madagascar was common as a result of lowered sea-level that would have allowed the formation of stepping-stone islands. Patterns of diversification that emerged from the scops-owls data are: 1) a star-like pattern concerning the order of colonization of the Indian Ocean islands and 2) the high genetic distinctiveness among all Indian Ocean taxa, reinforcing their recognition as distinct species.

Coevolutionary patterns and diversification of avian malaria parasites in African sunbirds (Family Nectariniidae)

The coevolutionary relationships between avian malaria parasites and their hosts influence the host specificity, geographical distribution and pathogenicity of these parasites. However, to understand fine scale coevolutionary host-parasite relationships, robust and widespread sampling from closely related hosts is needed. We thus sought to explore the coevolutionary history of avian Plasmodium and the widespread African sunbirds, family Nectariniidae. These birds are distributed throughout Africa and occupy a variety of habitats. Considering the role that habitat plays in influencing host-specificity and the role that host-specificity plays in coevolutionary relationships, African sunbirds provide an exceptional model system to study the processes that govern the distribution and diversity of avian malaria. Here we evaluated the coevolutionary histories using a multi-gene phylogeny for Nectariniidae and avian Plasmodium found in Nectariniidae. We then assessed the host-parasite biogeography and the structuring of parasite assemblages. We recovered Plasmodium lineages concurrently in East, West, South and Island regions of Africa. However, several Plasmodium lineages were recovered exclusively within one respective region, despite being found in widely distributed hosts. In addition, we inferred the biogeographic history of these parasites and provide evidence supporting a model of biotic diversification in avian Plasmodium of African sunbirds.

Mount Moco: its importance to the conservation of Swierstra's Francolin Pternistis swierstrai and the Afromontane avifauna of Angola

Summary The forests of the Angolan highlands are the smallest and most isolated of the Afromontane centres of endemism. Despite their high biodiversity value and small, fragmented extent of less than 200 ha, they remain entirely unprotected. Here we draw attention to their uniqueness and the threats to their conservation. We specifically highlight the importance of Mt Moco to bird conservation and describe current forest cover and condition. Sixty-four endemic/near-endemic species/subspecies and taxa with isolated populations are associated with the highlands of western Angola. All 19 forest-dependent taxa are among the 233 species recorded at Mt Moco, which include a rich diversity of montane specialists. Swierstra’s Francolin Pternistis swierstrai is the only threatened endemic. In 2009, 10 of 30 forest patches at Mt Moco larger than 0.5 ha were surveyed for this species. It occurred in seven of these surveyed patches, at a mean minimum density of 0.95 pair ha 1 in forest patches . 1 ha. Based on extrapolations of this figure, we estimate a minimum of 75 pairs of Swierstra’s Francolin at Mt Moco, and 185–420 pairs worldwide. Due to both limited range and small population size, we propose the species be up-listed from ‘Vulnerable’ to ‘Endangered’. Total forest cover at Mount Moco in forest patches . 0.5 ha in size is currently 85 ha. This is c.40% of the total cover of Afromontane forest estimated for Angola in 1974. Remaining forest cover at Mt Moco is being eroded by bush fires, removal of wood for fire and construction material, and clearance for subsistence agriculture by the c.330 inhabitants of Kanjonde village. In order to preserve the forest of Mt Moco, we propose the implementation of a protected area and define its boundaries. A similar proposal was made in 1974 for the creation of the Mount Moco Special Reserve.

Threatened birds of the Angolan Central Escarpment: distribution and response to habitat change at Kumbira Forest

Kumbira Forest is the best representative area of Angolas Central Escarpment and the only site known to hold significant populations of four of the five threatened endemic bird species of this habitat. However, the forest is disappearing as a result of human activities. Remote-sensing techniques were used to assess changes in forest cover, and bird and habitat surveys were performed to assess the effect of land-use changes on endemic species and the bird community. No relationships could be established between the presence of endemics and habitat and landscape variables. This lack of effect may be attributable to the low number of records and compounded by the mosaic structure of the landscape. Although forest cover has been maintained in Kumbira, old-growth forest has been replaced by secondary growth in many areas. Nevertheless these secondary-growth forest patches can maintain a bird community similar to that found in old-growth forest.

First record of Aedes albopictus (Skuse 1894) on São tomé island

Biological invasions have critical impacts on native biodiversity and human societies and especially on oceanic islands that are fragile and threatened ecosystems. The invasive tiger mosquito Aedes (Stegomyia) albopictus (Skuse, 1894) native to Southeast Asia has been introduced during the past 30 years almost everywhere in the world, including the Americas, the Pacific, Europe and Africa. It has been reported for the first time in the Gulf of Guinea in 2000, first in Cameroon, then in Bioko Island in 2003 and more recently in Gabon in 2007. Here we report the first record of Ae. albopictus on São Tomé Island. Although we cannot estimate precisely the year of introduction on São Tomé Island, it most likely arrived within the last 10 years. By sequencing the mitochondrial cytochrome c oxidase gene from individual adults, we detected three haplotypes already present in mainland Africa. More studies are needed to explore the dynamics of its expansion and competition with insular native mosquitoes.

The Namba mountains: new hope for Afromontane forest birds in Angola

Afromontane forest is the most localised and threatened habitat type in Angola. For the past 40 years the estimate of the area covered by this habitat in Angola has been c.200 ha. At present, 85 ha remain at Mt Moco, the most important known site to date. This habitat holds 20 bird taxa of conservation significance but some are now rare or absent at Mt Moco. Given the small extent of forest, its high conservation value and the severe human impacts on it, finding new areas of Afromontane forest is a high conservation priority. With this objective, we visited the Namba mountains in July 2010, where c.100 ha was thought to remain in the 1970s, to establish the extent and condition of forest there and to conduct bird surveys. We found closed-canopy Afromontane forest with an abundance of Podocarpus latifolius and little human disturbance. We recorded 89 bird species, 56 in or adjacent to forest and including all 20 priority taxa and a significant population of the Endangered Swierstra’s Francolin Pternistis swierstrai. On-screen digitising of forest patches using Google Earth indicates that the larger patches are an order of magnitude larger than at Mt Moco and that there is currently . 590 ha of forest in the Namba mountains, more than trebling the previous national estimate. The site qualifies as a new Important Bird Area and is a high priority for inclusion in Angola’s protected area network.

Rapid decline of the endemic giant land snail Archachatina bicarinata on the island of Príncipe, Gulf of Guinea.

Terrestrial and freshwater molluscs are amongst the most threatened of all taxa, yet data exist on the distribution and status of only a small proportion of the species. Here we present the results of the first systematic survey of a terrestrial mollusc on the island of Principe in the Gulf of Guinea. Archachatina bicarinata has never been previously surveyed, despite being categorized as Vulnerable on the IUCN Red List and suffering from unregulated harvesting for food. We found that A. bicarinata is restricted to primary rainforest and its abundance and probability of occurrence increased as surveyed sites became less accessi- ble. Additional anecdotal evidence from the observations of previous scientific expeditions, local guides and snail har- vesters suggested that the species has suffered a dramatic decline in population size and distribution in recent years. We therefore recommend that immediate action be taken to prevent its imminent extinction on Principe. The collection of A. bicarinata from protected areas should be banned, as should commercial harvesting and sales. Subsistence collect- ing should be limited to larger individuals. Our data have been used to inform the management plans for the protected areas on Principe and SaoT ome, and this should help to ensure the future of A. bicarinata on both islands.

Insularity effects on bird immune parameters: A comparison between island and mainland populations in West Africa

Abstract Oceanic islands share several environmental characteristics that have been shown to drive convergent evolutionary changes in island organisms. One change that is often assumed but has seldom been examined is the evolution of weaker immune systems in island species. The reduction in species richness on islands is expected to lead to a reduced parasite pressure and, given that immune function is costly, island animals should show a reduced immune response. However, alternative hypotheses exist; for example, the slower pace of life on islands could favor the reorganization of the immune system components (innate vs. acquired immunity) on islands. Thus far, few island species have been studied and no general patterns have emerged. Here, we compared two immune parameters of birds from São Tomé and Príncipe islands to those of their close relatives at similar latitudes on the mainland (Gabon, West Africa). On islands, the acquired humoral component (total immunoglobulins) was lower for most species, whereas no clear pattern was detected for the innate component (haptoglobin levels). These different responses did not seem to arise from a reorganization of the two immune components, as both total immunoglobulins and haptoglobin levels were positively associated. This work adds to the few empirical studies conducted so far which suggest that changes in immune parameters in response to insularity are not as straightforward as initially thought.

The collection of birds from São Tomé and Príncipe at the Instituto de Investigação Científica Tropical of the University of Lisbon (Portugal).

Abstract The former Instituto de Investigação Científica Tropical-IICT (Lisbon, Portugal), recently integrated into the University of Lisbon, gathers important natural history collections from Portuguese-speaking African countries. In this study, we describe the bird collection from the Democratic Republic of São Tomé and Príncipe, which was fully taxonomically checked and georeferenced. The IICT bird collection contains 5598 specimens, of which 559 are from São Tomé and Príncipe, representing 85 taxa, including 19 endemic species and 13 endemic subspecies of birds. The specimens were collected between 1946 and 1973, although 43% of the records are from 1954 and 45% are from 1970. The geographic distribution of samples covers the whole territory, with a higher number of records from São Tomé than from Príncipe. The districts with highest number of records are Pagué (equivalent to Príncipe Island), and Água Grande and Mé-Zochi on São Tomé. Despite the relatively low number of specimens per taxon, the importance of the collection is considerable due to the high number of endemic and threatened species represented. Furthermore, it adds valuable information to the GBIF network, especially for a country whose two islands are each an Endemic Bird Area and for which substantial gaps in ornithological knowledge remain.