Biology subjects

Falcon, W.

Publications and source records attributed to Falcon, W..

4 recordsLinked to original sources

bioRxiv2018

Breaking from the cage and taking over an island: Relentless increase and range expansion of white-winged parakeets in Puerto Rico

Introduced psittacine birds can become highly invasive. In this study, we assessed invasions of Psittaciformes in Puerto Rico. We reviewed the literature, public databases, citizen science records, and performed in situ population surveys across the island to determine the historical and current status and distribution of psittacine species. We used count data from Ebird to determine population trends. For species whose populations were increasing, we modelled their potential distribution using niche modeling techniques. We found 46 Psittaciformes in Puerto Rico, of which 26% are only present as pets, at least 29 species have been reported in the wild, and of those, there is evidence that at least 12 species are breeding. Our results indicate that most introduced species which have been detected as established still persist, although mostly in localized areas and small populations. Clear evidence of invasiveness was found for Brotogeris versicolurus and Myiopsitta monachus, which have greatly expanded their range in recent years. Psittacara erythrogenys and Eupsittacula canicularis also showed population increases, although to a lesser degree. The niche models predicted suitable areas for the four species, and also indicate the potential for range expansion. We discuss the factors leading to invasion success, assess the potential impacts, and we discuss possible management strategies and research prospects.

ecology↗

bioRxiv2018

Frugivory and seed dispersal by chelonians: A review and synthesis

In recent years, it has become clear that frugivory and seed dispersal (FSD) by turtles and tortoises is much more common than previously thought. Yet, a review and synthesis is lacking. We here review published and unpublished records of chelonian FSD, and assess the role of chelonians as seed dispersers, from individual species to the community level. We first discuss the distribution of chelonian FSD and the characteristics of the fruit and/or seed species eaten and dispersed by chelonians. We then use the seed dispersal efficiency framework to explore the quantitative and qualitative components of seed dispersal by tortoises and turtles, embarking on a journey from when the fruits and/or seeds are consumed, to when and where they are deposited, and assess how efficient chelonians are as seed dispersers. We finally discuss chelonian FSD in the context of communities and chelonians as megafauna. We found that a substantial proportion of the worlds aquatic and terrestrial turtles and a major part of testudinid tortoises (70 species in 12 families) include fruits and/or seeds in their diet, and that furits of at least 588 plant species in 120 families are ingested and/or dispersed by chelonians. For some chelonians, overall or in certain seasons, fruit may even form the largest part of their diet. Contrary to seed dispersal by lizards, the other major reptilian frugivores, chelonian FSD is not an island phenomenon in terms of geographic distribution. Nevertheless, on islands especially tortoises are often among the largest native terrestrial vertebrates--or were, until humans got there. We synthesize our knowledge of chelonian FSD, and discuss the relevance of our findings for conservation and restoration, especially in relation to rewilding with large and giant tortoises.\n\nResumenEn anos recientes, se ha hecho claro que la frugivoria y dispersion de semillas (FDS) llevada a cabo por tortugas (quelonidos) es mas comun de lo antes pensado. No obstante, todavia careciamos de una revision y sintesis sobre este tema. En este articulo, revisamos records (publicados y no publicados) sobre FDS por quelonidos, y evaluamos su rol como dispersores de semillas, desde el nivel de individuos, al nivel de comunidades. Primero, discutimos la distribucion de FDS por quelonidos, y las caracteristicas de las especies de frutos y/o semillas consumidas y dispersadas por tortugas. Luego hacemos uso del concepto de la eficiencia de dispersion de semillas como marco de referencia para explorar los componentes cualitativos y cuantitativos de la FDS por quelonidos, embarcandonos en un viaje desde cuando los frutos y/o semillas son consumidas, hasta cuando son depositadas. Tambien evaluamos cuan eficientes son los quelonidos como dispersores de semillas. Finalmente procedemos a discutir la FDS por quelonidos en el contexto de comunidades, y como megafauna. Encontramos que una proporcion substancial de las tortugas acuaticas del mundo y la mayor parte de las tortugas testudinidas (70 especies en 12 familias) incluyen frutos y/o semillas en su dieta que abarcan al menos 588 especies de plantas en 120 familias. En algunas especies, en general o en algunas estaciones, la mayor parte de su dieta esta conformada por frutas y/o semillas. Mas importante aun, y contrario a las lagartijas, que son otro grupo importante de reptiles que incurre en FDS, la frugivoria y dispersion de semillas por quelonidos no es un fenomeno de islas solamente, en terminos de distribucion geografica. Empero, en islas, especialmente las tortugas terrestres, estan entre los vertebrados nativos de mayor tamano-o lo estuvieron, hasta que los humanos llegaron a ellas. En este articulo, hacemos una sintesis de las lecciones aprendidas hasta ahora sobre la FDS por quelonidos, y discutimos la relevancia de nuestros hallazgos para la conservacion y restauracion, especialmente en relacion a proyectos de resilvestrar ( rewilding) con tortugas gigantes o de gran tamano.

ecology↗

bioRxiv2018

From the cage to the wild: Introductions of Psittaciformes to Puerto Rico with emphasis on the invasive ecology of the white-winged parakeet

In this study, we assessed invasions of Psittaciformes in Puerto Rico. We reviewed the literature, public databases, citizen science records, and performed in situ population surveys across the island to determine the historical and current status and distribution of psittacine species. We used count data from Ebird to determine population trends. For species whose populations were increasing, we modelled their potential distribution using niche modeling techniques. Focusing on the white-winged parakeet (Brotogeris versicolurus), which was considered the most successful psittacine species by the year 2000, we evaluated the population size, calculated growth rates and estimated the breeding proportion in two populations by performing roost counts for four consecutive years. We found a total of 46 Psittaciformes present in Puerto Rico, of which 26% are only present as pets, at least 29 species have been reported in the wild, and of those, there is evidence that at least 12 species are breeding. Our results indicate that most introduced species which have been detected as established still persist, although mostly in localized areas and small populations. Clear evidence of invasiveness was found for B. versicolurus and Myiopsitta monachus, which have greatly expanded their range. Moreover, Psittacara erythrogenys and Eupsittacula canicularis also showed population increase. The niche models predicted suitable areas for the four species, and also indicate the potential for range expansion. Population estimates of the white-winged parakeet during the study period showed a steady increase, and exhibited exponential growth, with geometric mean population growth rates of 1.25 per year. Currently growth rate of the white-winged parakeet does not appear to be limited by any predator, resources or nest availability, and we expect them to continue increasing and expanding their range. We discuss the factors leading to invasion success, assess the potential impacts, and we discuss possible management strategies and research prospects.

ecology↗

bioRxiv2017

Neural Networks for Efficient Bayesian Decoding of Natural Images from Retinal Neurons

Decoding sensory stimuli from neural signals can be used to reveal how we sense our physical environment, and is valuable for the design of brain-machine interfaces. However, existing linear techniques for neural decoding may not fully reveal or exploit the fidelity of the neural signal. Here we develop a new approximate Bayesian method for decoding natural images from the spiking activity of populations of retinal ganglion cells (RGCs). We sidestep known computational challenges with Bayesian inference by exploiting artificial neural networks developed for computer vision, enabling fast nonlinear decoding that incorporates natural scene statistics implicitly. We use a decoder architecture that first linearly reconstructs an image from RGC spikes, then applies a convolutional autoencoder to enhance the image. The resulting decoder, trained on natural images and simulated neural responses, significantly outperforms linear decoding, as well as simple point-wise nonlinear decoding. These results provide a tool for the assessment and optimization of retinal prosthesis technologies, and reveal that the retina may provide a more accurate representation of the visual scene than previously appreciated.

neuroscience↗