How to predict the future? On niches and potential distributions of amphibians and reptiles in a changing climate

The present Ph.D. thesis investigates relationships between variations in large scale climate, niches of amphibians and reptiles and their corresponding geographic distribution patterns. As suggested by several authors, anthropogenic climate change may threaten a large part of the world’s biota. However, our knowledge on processes leading to those threats and our ability to make robust predictions of possible impacts is still limited but pivotal to develop successful management strategies. The aim of the thesis at hand is to narrow some of those knowledge gaps. The results are presented in four sections, each with several complementary chapters focussing on several aspects of the link between macro-climate, species’ environmental niches and their distribution patterns. Each chapter is distinct in the question elucidated and the material and methods used to answere these questions. Section 1 The first section provides a general overview over the current knowledge concerning impacts of climate change on biota, niche concepts, availability of both climate and species occurrence data and the methods used herein. Additionally, potential ‘pitfalls’ when applying environmental niche models or climate envelope models are highlighted, illustrated and discussed using numerous examples. Section 2 This section focuses on the structure of climate niches. Climatic variability within species ranges and habitat choice are analysed and dicussed in the context of natural history properties of the respective species. Chapter 2.1. Climate is suggested to be one major driver shaping species range patterns. Especially species with temperature-dependent sex determination may depend on certain climatic conditions, such as the Slider, Trachemys scripta, from North America. In this chapter, we hypothesise that climatic requirements allowing successful egg incubation and balanced sex ratios in T. scripta are the major driver for the species’ geographic distribution. We tested if the observed variation in monthly mean temperatures at 377 records throughout the native distribution of T. scripta can be used as a predictor for its geographic range. Our study showed that apparently climatic requirements during egg-incubation are the major driver for the species’ geographic distribution. Freezing events during winter may regionally limit the species’ distribution only. Adaptive strategies such as nest site choice by females, plasticity in nesting phenology or regional variation in embryonic temperature sensitivity exist. However, they may account only for partial compensation of negative effects caused by regional differences in temperature related parameters or a changing climate. Chapter 2.2. Recently, several authors observed a climatic mismatch between native and invasive ranges predicted by Climate Envelope Models (CEMs). In chapter 2.2, we address the issue of niche shift in alien invasive species versus variable choice by deriving CEMs based on multiple variable sets. The first selection of predictors aims at representing the physiological limits of a well studied alien invasive Slider. This model was compared to numerous other models based on various subsets of environmental variables or aiming at comprehensiveness. The CEMs aiming to represent the species physiology depicts its worldwide potential distribution better than any of the other approaches. The results indicate that a natural history driven understanding is crucial in developing statistical models of niches while ‘comprehensive’ or ‘standard’ sets of explanatory variables may be of limited use. Chapter 2.3. The use of Climate Envelope Models (CEMs) to predict potential distributions of species is steadily increasing. A necessary assumption is that climatic niches are rather conservative, but recent findings of niche shifts during biological invasion indicate that this assumption is not valid in every case. Selection of predictor variables may be one reason for observed shifts. In chaper 2.3, we assess differences in climatic niches in the native and invaded ranges of the Mediterranean Housegecko (Hemidactylus turcicus) in terms of commonly applied climate variables in CEMs. We analyzed which variables are more conserved versus relaxed (i.e. subject to niche shift). Furthermore, we study the predictive power of different sets of climate variables. We developed models for the Mediterranean region and the conterminous United States (US) using MaxEnt and various subsets of variables out of 19 environmental layers. Occurrence data from the native range in the Mediterranean region were used to predict the introduced range in the US and vice versa. Niche similarity and conservatism per predictor and per set of predictor as assessed using both Hellinger distances and Schoener’s index. Significance of results was tested using null models. My results indicate that the degree of niche similarity and conservatism varied greatly among predictors and variable sets applied. Shifts observed in some variables can be attributed to active habitat selection whereby others apparently reflect background effects. The study was based on comprehensive occurrence data from all regions where Hemidactylus turcicus is present in Europe and North and Central America providing a robust fundament. My results indicate that the degree of niche similarity and conservatism varied greatly among predictors and variable sets applied. These results have important implications for studies of biological invasion, impacts of climate change, and niche evolution. Section 3 This part of the thesis at hand focus on the relative importance of dispersal abilities, accessibility and biotic interactions shaping a species’ realized distribution. Chapter 3.1. Globalization has led to a heightened spread of alien invasive species, which can alter mutualistic relationships, community dynamics, ecosystem function, and resource distributions. They can cause extinctions affecting thereby local and global diversity. Among reptiles two gecko species, Hemidactylus frenatus and Hemidactylus mabouia, have considerably increased their range during the last century. Both have caused already local decimations and extinctions of native species. Records of invasive populations of H. frenatus are known from tropical Asia through Central America and Florida and invasive populations of H. mabouia can be found in Central and Southern Africa as well as in large parts of Central and South America. Only few sympatric populations are known. Herein, we aim to identify areas potentially suitable for the geckos using a climate envelope approach, predict their potential distribution under current conditions and a future climate change scenario, and try to assess why sympatric populations of both geckos are apparently rare. The results presented in chapter 3.1 suggest that climatic suitable areas for both species can be found in nearly all tropical regions. Future projections revealed that the amount of climatic suitable areas will increase for H. frenatus on a global scale, but decrease for H. mabouia. Greatest changes are suggested for South America where further spreading of H. frenatus will be enhanced due to better climatic conditions. In contrast, climatic conditions for H. mabouia will be aggravated here. We conclude that both competitive exclusion and a non equilibrium in the ranges of the species explain the virtual absence of sympatric populations, although the impact of climate on competition success is pending further testing in the field. Chapter 3.2. It was suggested that Climate Envelope Models may be only of limited use if the target species’ range is not predominately limited by unsuitable climate. In chapter 3.2, I test this assumption using the alien invasive anuran Eleutherodactylus coqui as model species. This species is presently distributed in many Caribbean islands and Hawaiian Islands where it causes major ecological and socioeconomic problems, especially evident in the later. I use a maximum entropy ecological niche modeling approach to model the native geographic distribution of this species and to project that model into other potentially threatened areas. The projection results under current climatic conditions suggested high probabilities of occurrence in tropical regions including the Caribbean, Florida, major parts of the Amazon basin and adjacent Andes, the Pantepui region, the Congo basin, and most Asian islands. Using only native records within Puerto Rico for model training my results indicate that the invasive range in the Hawaiian Islands can be predicted with high acurrancy. Projections of potential distributions under future anthropogenic global warming scenarios within the Hawaiian Islands suggest an overall stable potential distribution, but fine scale patterns suggest a possible range allocation towards higher elevations which may affect natural reserves. If the predictive maps are interpreted as depicting invasiveness potential of E. coqui, strategies to prevent further invasion should focus on biosafety measurements within the areas highlighted. Chapter 3.3. In this chapter, the invasive alien Cuban treefrog Osteopilus sepentrionalis native to Cuba, the Bahamas and some adjacent islands was used as an second example for the case that climate is not the predominantly driver of the range. It was accidentally introduced to Florida, Puerto Rico and some Hawaiian islands; it has become predator and competes with native wildlife. In chapter 3.3, we have used a maximum entropy ecological niche modelling approach to model its potential spread derived from present climate conditions as present in its native geographic distribution and we project that model into future climate change scenarios in order to detect new areas that are potentially threatened. Our model applying current climatic conditions suggested high probabilities of occurrence in countries around the Gulf of Mexico. As in chapter 3.2, the results indicate that the invasive range in Florida can be predicted with high acurrancy using only native records within Cuba and the Bahamas for model training if the predictor variables are carefully chosen. Chapter 3.4. Biotic interactions such as competitive exclusion or predation may limit the realized distribution of species in some areas although climatic conditions are well suitable. In chapter 3.4 we assess such a pattern as observed in the Brown tree snake (Boiga irregularis). The snake is native to South-East Asia and Australia and has been introduced to Guam. Here it causes major ecological and socioeconomic problems and is considered to belong to the 100 worldwide worst alien invasive species. We use a maximum entropy-based Climate Envelope Model to identify areas outside the species’ known range which worldwide are potentially suitable under current climate. Projections revealed that this invasive alien species potentially occurs in tropical and in part subtropical regions. In the larger vicinity of the snake’s known distribution, highest suitability was found for the Northern Mariana and Hawaiian Islands, Madagascar, New Caledonia and Fiji Islands. However, although most East Asian mainlands and islands are climatically suitable the invasive populations of this species do virtually not exist. The predicted potential distribution is highly coincident with the general distribution of the genus Boiga. Since B. irregularis does not coexist with other members of the genus or other potential competitors in its native range, competitive exclusion may be the best explaination for the observed pattern. Chapter 3.5. Anthropogenic habitat alteration has a strong impact on native biota and can significantly shape distribution patterns. Eleutherodactylus johnstonei, native to the northern lesser Antilles, has established numerous invasive populations at Caribbean islands and the adjacent Central and South American mainland. The species is a highly successful colonizer, but only able to invade anthropogenic disturbed habitats. Here, I use a maximum entropy climate envelope modelling approach to model the geographic distribution of this species and to project that model into other potentially threatened areas. Results obtained from the model are compared with a measure of anthropogenic habitat disturbance (Human Footprint). My results suggest a high probability of occurrence in large parts of southern Central America, at the northern and north-eastern coast of South America, and in the Andes of Colombia, Ecuador and Venezuela. The Andean region harbouring a diverse amphibian fauna, which is highly threatened due to anthropogenic habitat alteration, appears to be at highest risk for further spread. If the predictive maps are interpreted as depicting invasiveness potential of E. johnstonei, strategies to prevent further invasion should focus on biosafety measurements within the areas highlighted. Section 4 The focus of the last section are the breadths of climate niches, their evolution and dynamics in space and time. Chapter 4.1. If climate changes a species’ range may shift as a respond. If disprersal limitations exist hampering range shifts, the species’ range may (1) shrink, (2) the species’ niche breadth may be large enough to buffer changing environmental conditions, or (3) the species may adapt to them. In chapter 4.1 we use a gecko endemic to a small island as a case study. Phelsuma parkeri is an endemic gecko species native to the relatively flat island of Pemba (elevational range 0 to Chapter 4.2. The disturbance vicariance hypothesis (DV) has been proposed to explain speciation in Amazonia, especially its edge regions, e.g. in Guianan harlequin frogs (Atelopus) having derived from a cool-adapted Andean/western Amazonian ancestor. In this chapter, in concordance with DV predictions, we expected that: (i) these amphibians display a natural distribution gap in central Amazonia; (ii) east of this gap they constitute a monophyletic lineage which is nested within in a pre-Andean/western clade; (iii) climate envelopes of Atelopus west and east of the distribution gap show some macroclimatic divergence due to regional climate envelope shift; (iv) geographic distributions of climate envelopes of western and eastern Atelopus range into central Amazonia but with limited spatial overlap. We tested if presence and apparent absence data points of Atelopus were homogenously distributed applying Ripley’s K function. A molecular phylogeny (mitochondrial 16S rRNA gene), by application of Maximum Likelihood and Bayesian Inference, was reconstructed to study if Guianan Atelopus constitute a nested clade within a larger genus phylogeny. We focussed on climate envelope divergence and geographic distribution by computing climatic envelope models with MaxEnt based on macroscale bioclimatic parameters and testing them with using Schoener’s index and modified Hellinger distance. All four expectations were corroborated leading us to conclude that DV predictions are well applicable to Amazonian harlequin frogs. We here for the first time draw attention to species’ climate envelope change and assessment in the ongoing debate on diversification and distributions in the Amazon basin and adjacent areas. General conclusions The results of this Ph.D. thesis, while updating our status of knowledge on the link between climate change and corresponding responses of species in terms of changes in their phenology and / or their distribution patterns, hopefully will enhance our ability to understand and probably manage some of the problems arising due to anthropogenic climate change. However, although our qualitative understanding of processes and mechanims causing patterns of species phenology and distribution has been largely extended during the last decades, it is still far from being comprehensive and our ability to make robust quantitative predictions is still very limited

Potential worldwide impacts of sea level rise on coastal-lowland anurans

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Amphibians are the most severely threatened terrestrial vertebrates and we are witnessing a global decline phenomenon, which is even suggested to be of the same level as the historical mass extinctions. Albeit the myriad of causative stressors identified in the last decades, future sea level rise (SLR) and its impact on coastal terrestrial fauna remains essentially unreported. Even if there is no consensus on the magnitude of the future SLR, several studies suggest that it is likely to be greater than previously reported by the Fourth Assessment Report (AR4) of the Intergovernmental Panel on Climate Change (IPCC). Therefore, it is reasonable to expect severe impacts on the coastal terrestrial fauna at a worldwide scale. Here, we assembled a worldwide data set of coastal-lowland anuran species in an attempt to quantify the potential habitat loss caused by flooding according to different SLR scenarios. We also assessed potential habitat suitability under climate change (CC) in order to evaluate its expected effects on species' climatic niches, by building species distribution models for three future scenarios (A2a, A1b and B2a). Our results revealed that SLR has the potential to produce negative impacts on similar to 86% of the selected coastal-lowland species in different magnitudes, whereas CC is expected to produce a greater impact on the same taxa. Thus, species predicted to persist under the new climatic conditions may be exposed to effects associated with SLR. Breaking our results down to biogeographic realms, we found that Australasia harboured most amphibian species suffering the dual impacts of SLR and CC. Based on our results, we advocate for the inclusion of potential future impacts of SLR in conservation action plans, anticipating and preventing biodiversity loss.Amphibians are the most severely threatened terrestrial vertebrates and we are witnessing a global decline phenomenon, which is even suggested to be of the same level as the historical mass extinctions. Albeit the myriad of causative stressors identified12191101CNQP - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOCAPES - COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIORFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOConselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)161812/2011-23855/2013- 92011/51694-7405285/2013-2302589/2013-9We thank Rafael Loyola, Jean Vitule, Faraham Ahmadzadeh, Adriele Oliveira, and Guilherme Becker for their suggestions and contributions. ISO is grateful to Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq: 161812/2011-2) and Coordenaçã

Predicting terrestrial dispersal corridors of the invasive African clawed frog Xenopus laevis in Portugal

Invasive species, such as the mainly aquatic African clawed frog Xenopus laevis, are a main threat to global biodiversity. The identification of dispersal corridors is necessary to restrict further expansion of these species and help to elaborate management plans for their control and eradication. Here we use remote sensing derived resistance surfaces, based on the normalised difference vegetation index (NDVI) and the normalised difference water index (NDWI) accounting for behavioural and physiological dispersal limitations of the species, in combination with elevation layers, to determine fine scale dispersal patterns of invasive populations of X. laevis in Portugal, where the frog had established populations in two rivers. We reconstruct past dispersal routes between these two invaded rivers and highlight high risk areas for future expansion. Our models suggest terrestrial dispersal corridors that connect both invaded rivers and identify artificial water bodies as stepping stones for overland movement of X. laevis. Additionally, we found several potential stepping stones into novel areas and provide concrete information for invasive species management.info:eu-repo/semantics/publishedVersio

Diversity and habitat use of snakes from the coastal Atlantic rainforest in northeastern Bahia, Brazil

The north coast of Bahia comprises a 220 km long region within the Atlantic rainforest ecoregion. Studies focusing on snake communities are still scarce in this part of the state of Bahia. In this study, we assess snake diversity at nine locations, including habitat use and activity patterns. The sites were surveyed for three years, and four museum collections were visited to compile additional data. We obtained information on 50 species from 774 specimens. While the snake fauna at Instituto da Mata contained the greatest richness with 15 observed species, the snake fauna at Imbassaí exhibited the greatest snake diversity due to a lower dominance. The estimated species richness of the region might be as many as 55 species. Snakes occurred mainly in the restinga ecosystem (N = 27), followed by ombrophilous forest (N = 25), and consisted mainly of terrestrial species. The restinga dry forest is home to most species, however some are restricted to habitats in other vegetation types related to their biology. The snake assemblage on the north coast of Bahia is similar to others in the Atlantic rainforest and Caatinga domain in northeastern Brazil

Using indicator species to detect high quality habitats in an East African forest biodiversity hotspot

AbstractSpecies demanding specific habitat requirements suffer, particularly under environmental changes. The smallest owl of Africa, the Sokoke Scops Owl (Otus ireneae), occurs exclusively in East African coastal forests. To understand the movement behaviour and habitat demands of O. ireneae, we combined data from radio-tracking and remote sensing to calculate Species Distribution Models across the Arabuko Sokoke forest in southern Kenya. Based on these data, we estimated the local population size and projected the distribution of current suitable habitats. We found that the species occurs only in Cynometra woodland with large old trees and dense vegetation. Based on home range sizes and the distribution of suitable forest habitats, the local population size was estimated at < 400 pairs. Ongoing selective logging of hard-wood trees and the production of charcoal are reducing habitat quality of which will reduce the low numbers of O. ireneae, and of other specialist forest species, even further. Due to their close connection with intact Cynometra forest, O. ireneae is an excellent indicator of intact forest remnants. In addition, this species is a suitable flagship for the promotion and conservation of the last remaining coastal forests of East Africa

More time for aliens? Performance shifts lead to increased activity time budgets propelling invasion success

© 2022 The Authors. Published by Springer. This is an open access article available under a Creative Commons licence. The published version can be accessed at the following link on the publisher’s website: https://doi.org/10.1007/s10530-022-02903-6In the Grinnellian niche concept, the realized niche and potential distribution is characterized as an interplay among the fundamental niche, biotic interactions and geographic accessibility. Climate is one of the main drivers for this concept and is essential to predict a taxon’s distribution. Mechanistic approaches can be useful tools, which use fitness-related aspects like locomotor performance and critical thermal limits to predict the potential distribution of an organism. These mechanistic approaches allow the inclusion key ecological processes like local adaptation and can account for thermal performance traits of different life-history stages. The African Clawed Frog, Xenopus laevis, is a highly invasive species occurring on five continents. The French population is of special interest due to an ongoing expansion for 40 years and a broad base of knowledge. We hypothesize that (1) the French population exhibits increased activity time in the invasive European range that could be devoted to fitness-relevant activity and (2) tadpoles may have less activity time available than adult frogs from the same range. We investigate how thermal performance traits translate into activity time budgets and how local adaptation and differences in the thermal responses of life-history stages may boost the European Xenopus invasion. We use a mechanistic approach based on generalized additive mixed models, where thermal performance curves were used to predict the hours of activity and to compare the potential activity time budgets for two life-history stages of native and invasive populations. Our results show that adult French frogs have more activity time available in Europe compared to South African frogs, which might be an advantage in searching for prey or escaping from predators. However, French tadpoles do not have more activity time in Europe compared to the native South African populations suggesting that tadpoles do not suffer the same strong selective pressure as adult frogs.Open Access funding enabled and organized by Projekt DEAL. This work was supported by the ERANET BiodivERsA grant INVAXEN, with the national funders Agence Nationale de la Recherche (ANR), Deutsche Forschungsgemeinschaft (DFG), Belgian Federal Science Policy Office (BELSPO), and Fundaçao para a Ciencia e a Tecnologia (FCT), as part of the 2013 BiodivERsA call for research proposals. INVAXEN “Invasive biology of Xenopus laevis in Europe: ecology, impact and predictive models”. CW, NK, MM and JM thank the DSI-NRF Centre of Excellence for Invasion Biology (South Africa) and the National Research Foundation of South Africa (NRF Grant No. 87759 to JM). NK would like to acknowledge the Ambassade de France en Afrique du Sud (France). This study was part of the project Life Control Strategies of Alien Invasive Amphibians (CROAA)—LIFE15 NAT/FR/000864 funded by the Life program of the European Commission.Published onlin

Final countdown for biodiversity hotspots

Most of Earth's biodiversity is found in 36 biodiversity hotspots, yet less than 10% natural intact vegetation remains. We calculated models projecting the future state of most of these hotspots for the year 2050, based on future climatic and agroeconomic pressure. Our models project an increasing demand for agricultural land resulting in the conversion of >50% of remaining natural intact vegetation in about one third of all hotspots, and in 2-6 hotspots resulting from climatic pressure. This confirms that, in the short term, habitat loss is of greater concern than climate change for hotspots and their biodiversity. Hotspots are most severely threatened in tropical Africa and parts of Asia, where demographic pressure and the demand for agricultural land is highest. The speed and magnitude of pristine habitat loss is, according to our models, much greater than previously shown when combining both scenarios on future climatic and agroeconomic pressure

Alien Invasive Slider Turtle in Unpredicted Habitat: A Matter of Niche Shift or of Predictors Studied?

BACKGROUND: Species Distribution Models (SDMs) aim on the characterization of a species' ecological niche and project it into geographic space. The result is a map of the species' potential distribution, which is, for instance, helpful to predict the capability of alien invasive species. With regard to alien invasive species, recently several authors observed a mismatch between potential distributions of native and invasive ranges derived from SDMs and, as an explanation, ecological niche shift during biological invasion has been suggested. We studied the physiologically well known Slider turtle from North America which today is widely distributed over the globe and address the issue of ecological niche shift versus choice of ecological predictors used for model building, i.e., by deriving SDMs using multiple sets of climatic predictor. PRINCIPAL FINDINGS: In one SDM, predictors were used aiming to mirror the physiological limits of the Slider turtle. It was compared to numerous other models based on various sets of ecological predictors or predictors aiming at comprehensiveness. The SDM focusing on the study species' physiological limits depicts the target species' worldwide potential distribution better than any of the other approaches. CONCLUSION: These results suggest that a natural history-driven understanding is crucial in developing statistical models of ecological niches (as SDMs) while "comprehensive" or "standard" sets of ecological predictors may be of limited use