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- Institut für Integrierte Naturwissenschaften, Abt. Biologie (29) (remove)
In the present study the flora and vegetation of Kakamega Forest, an East African rainforest in Western Kenya, was investigated. Kakamega Forest is highly degraded and fragmented and is an ideal model to study the anthropogenic influence on the forest inventory. The main focus was to analyse the influence of human impact on the vascular plant species composition. During five field phases in the years 2001 to 2004 a total of 19 study sites scattered over the whole forest including all fragments were investigated regarding forest structure, species composition and plant communities. The different forest sites were analysed by three different methods, phytosociological relevés, line-transect and with the variable-area transect method. The forest survey revealed about 400 taxa of vascular plant species, among them 112 trees, 62 shrubs, 58 climbers and 114 herbs. Several species are restricted to this forest in Kenya, but only one endemic species, the herb Commelina albiflora, could be discovered. About 15 species were recorded as new for Kenya and probably at least one species is new to science. Kakamega Forest is a unique mixture of Guineo-Congolian and Afromontane floral elements. About one half of the vascular plant species has its origin in the lowland forests of the Congo basin and one third originates from Afromontane habitats. The present study represents the first description of plant communities of Kakamega Forest. An analysis of different forest sites and plantations resulted in 17 different vegetation units. For the mature forest sites eleven plant communities were described. The young succession stage consists of two plant communities. Since the disturbance history and the age of the different plant communities could be estimated, their chronology was also described. An exception are the study sites within the plantations and afforested sites. The four defined vegetation units were not described as plant communities, because they are highly affected by man and do not belong to the natural succession of Kakamega Forest. Nevertheless, the regeneration potential of such forests was investigated. Due to the different succession stages the changing species composition along a disturbance gradient could be analysed. Most of Kakamega Forest consists of middle-aged secondary forest often surrounded by very young secondary forest. A true primary rainforest could not be found due the massive influence by over-exploitation. In all parts of the forest the anthropogenic influence could be observed. The forest develops towards a climax stage, but a 2 Abstract comparison with former surveys shows that the regeneration is much slower than expected. Human impact has to be avoided to allow the forest to develop into a primary-like rainforest. But several climax tree species might be missing anyway, because after the broad logging activities in the past there are not enough seed trees remaining. Species richness was highest in disturbed forest sites. A mixture of pioneer, climax and bushland species could be recorded there. Therefore, a high species richness is not a suitable indicator for forest quality. The proportion of climax species typical for Kakamega Forest would be a better measure. Compared to the main forest block the forest fragments do not lack in diversity as expected due to fragmentation processes. Instead, the only near primary forest could be recorded in Kisere, a northern fragment. The high amount of climax species and the more or less undisturbed forest structure is a result of the strict protection by the Kenya Wildlife Service and due to low logging activities. Differences in species composition between the studied forest sites are either a result of the different logging history or management regime rather than due to different edaphic or climatic conditions.
The implementation of physiological indicators reflecting the response of organisms to changes in their environment is assumed to provide potential benefits for ecological studies. By analysing the physiological condition of organisms in freshwater ecological studies rather than their ultimate effects, physiological indicators can contribute to a faster assessment of effects than using traditional ecological indicators, such as the evaluation of the benthic community structure or the determination of the reproductive success of organisms. This can increase the effectiveness of environmental health assessment and experimental ecology. In this respect the thesis focuses on physiological measures characterizing the energetic condition and energy consumption (the concentration of energy storage compounds, the adenylate energy charge, the energy consumption in vivo), as well as individual growth (RNA:DNA ratio) of organisms. Although these sub-individual indicators are commonly applied in marine ecology and more recently in ecotoxicology, they have been rarely applied in freshwater ecology to date. With respect to an increased use of physiological indicators in freshwater ecological studies, the objectives of the present thesis are twofold. First, it highlights the potential of assessing the individual fitness by means of physiological indicators in freshwater ecological studies. For that reason, Chapter 2 provides the basic assumptions as well as the theoretical and methodological fundamentals necessary for the application of physiological indicators within freshwater ecology and, furthermore, points out their applicability by several case studies. As second objective, the thesis addresses selected ecophysiological aspects of native and non-native freshwater amphipods, which are considered suitable candidates for the determination of physiological indicators in ecological studies due to their function as keystone species within aquatic habitats. The studies presented in Chapters 3−5 of the thesis provide information on (i) species- and sex-specific seasonal variations within the energetic condition of natural Gammarus populations (G. fossarum, G. pulex), (ii) differences in metabolic activity and behaviour between different amphipod species (G fossarum, G. roeselii and D. villosus), as well as (iii) the direct effects of ambient ammonia on the physiology and behaviour of D. villosus. The fundamental conclusions drawn from the conducted field and laboratory studies, as well as their relevance and general implications for the application of physiological indicators in freshwater ecological research are discussed in Chapter 6.
Eine Ursache des Insektenrückgangs ist die Abnahme der für Arthropoden wichtigen Lebensräume. Der kleinstrukturierte Obstanbau als Dauerkultur mit vielfältigen Strukturen (Bäume, Grünland, offener Boden) kann als Refugium wirken. Gerade Dauerkulturen, welche über viele Jahre bestehen bleiben, können einen großen ökologischen Wert für Insekten und Spinnentiere darstellen, wenn die negativen Einflüsse der Bewirtschaftung durch gezielte Maßnahmen minimiert werden. Im Gegensatz zu den gut untersuchten Streuobstwiesen liegen bisher nur wenige oder ungenaue Daten über die Arthropodenfauna in Erwerbsobstanlagen vor. Ziele dieser Arbeit sind eine genauere Erfassung der Arthropodenfauna in Erwerbsobstanlagen, Benennung der Einflussfaktoren und Erarbeitung einer indikatorgestützten Bewertungsmethode mit Entwicklung von Maßnahmen zur Förderung der Biodiversität. Es wurde eine intensive Erfassung der Insekten und Spinnentiere auf Basis von Individuenzahlen, Verteilung der Tiere auf Großgruppen, Artenzahlen der Käfer (inkl. Rote Liste) und Wanzen, deren Diversität und der sie beeinflussenden Faktoren auf vier Erwerbsobstflächen und einer Streuobstwiese als Referenzfläche in der Gemeinde Zornheim (Rheinland-Pfalz) untersucht. Mittels des erarbeiteten Bewertungsbogens wurden die Auswirkungen der fünf Faktorenkomplexe: Sonderstrukturen, Anlagenstruktur, Beschattung, Mahdregime und Einsatz von Pflanzenschutzmitteln auf die Arthropodenfauna erhoben und die auf der Fläche zu erwartende Biodiversität ermittelt. Die visuelle Darstellung der Einflussfaktoren mit Netzdiagrammen zeigt biodiversitätsbeeinträchtigende Faktoren und ermöglicht so Empfehlungen zur Aufwertung der Biodiversität. Die Bewertungsmethode kann nach Verifizierung im Rahmen von erfolgsorientierten Agrarumwelt- und Klimamaßnahmen (AUKM), zur Anerkennung von Kompensationsmaßnahmen (z.B. PIK) und zur Ermittlung des ökologischen Wertes (Ökosystemdienstleistung) von Obstanlagen genutzt werden. In modifizierter Form könnte es ebenfalls im Bereich der Flächenbewertung in Landschafts- und Bauleitplanung eingesetzt werden.
The diversity within amphibian communities in cultivated areas in Rwanda and within two selected, taxonomically challenging groups, the genera Ptychadena and Hyperolius, were investigated in this thesis. The amphibian community of an agricultural wetland near Butare in southern Rwanda comprised 15 anuran species. Rarefaction and jackknife analyses corroborated that the complete current species richness of the assemblage had been recorded, and the results of acoustic niche analysis suggested species saturation of the community. Surveys at many other Rwandan localities showed that the species recorded in Butare are widespread in cultivated and pristine wetlands. The species were readily distinguishable using morphological, bioacoustic, and molecular (DNA barcoding) features, but only eight of the 15 species could be assigned unambiguously to nominal species. The remaining represented undescribed or currently unrecognized taxa, including three species of Hyperolius, two Phrynobatrachus species, one Ptychadena species, and one species of Amietia. The diversity of the Ridged Frogs in Rwanda was investigated in two studies (Chapters III and IV). Three species of Ptychadena were recorded in wetlands in the catchment of the Nile. They can be distinguished by morphological characters (morphometrics and qualitative features) as well as by their advertisement calls and genetics. The Rwandan species of the P. mascareniensis group was shown to differ from the topotypic population as well as from other genetic lineages in sub-Saharan Africa and an old available name, P. nilotica, was resurrected from synonymy for this lineage. Two further Ptychadena species were identified among voucher specimens from Rwanda deposited in the collection of the RMCA, P. chrysogaster and P. uzungwensis. Morphologically they can be unambiguously distinguished from each other and the three other Rwandan species. A key based on qualitative morphological characters was developed, which allows unequivocal identification of specimens of all species that have been recorded from Rwanda. DNA was isolated from a Rwandan voucher specimen of P. chrysogaster, and the genetic analysis corroborated the species" distinct status.
A species of Hyperolius collected in the Nyungwe National Park was compared to all other Rwandan species of the genus and to morphologically or genetically similar species from neighbouring countries. Its distinct taxonomic status was justified by morphological, bioacoustic, and molecular evidence and it was described as a new species, H. jackie. A species of the H. nasutus group collected at agricultural sites in Rwanda was described as a new species in the course of a revision of the species of the Hyperolius nasutus group. The group was shown to consist of 15 distinct species which can be distinguished from each other genetically, bioacoustically, and morphologically.
The aerial performance, i.e. parachuting, of the Disc-fingered Reed Frog, Hyperolius discodactylus, was described. It represents a novel observation of a behaviour that has been known from a number of Southeast Asian and Neotropical frog species. Parachuting frogs, including H. discodactylus, exhibit certain morphological characteristics and, while airborne, assume a distinct posture which is best-suited for maneuvering in the air. Another study on the species addressed the validity of the taxon H. alticola which had been considered either a synonym of H. discodactylus or a distinct species. Type material of both taxa was re-examined and the status of H. alticola reassessed using morphological data from historic and new collections, call recordings, and molecular data from animals collected on recent expeditions. A northern and a southern genetic clade were identified, a divide that is weakly supported by diverging morphology of the vouchers from the respective localities. No distinction in advertisement call features could be recovered to support this split and both genetic and morphological differences between the two geographic clades are marginal and not always congruent and more likely reflect population-level variation. Therefore it was concluded that H. alticola is not a valid taxon and should be treated as a synonym of H. discodactylus.
The ongoing loss of species is a global threat to biodiversity, affecting ecosystems worldwide. This also concerns arthropods such as insects and spiders, which are especially endangered in agricultural ecosystems. Here, one of the main causing factors is management intensification. In areas with a high proportion of traditionally managed grassland, extensive hay meadows that are cut only once per year can still hold high levels of biodiversity, but are threatened by conversion into highly productive silage grassland. The Westerwald mountain range, western Germany, is such a region. In this thesis, I compare the local diversity of bees, beetles, hoverflies, leafhoppers, and spiders of five grassland management regimes along a gradient of land-use intensity. These comprise naturally occurring grassland fallows, three types of traditionally managed hay meadows, and intensively used silage grassland. By using three different sampling methods, I recorded ground-dwelling, flower-visiting, and vegetation-dwelling species. The results show that in most cases species richness and diversity are highest on fallows, whereas variation among different managed grassland types is very low. Also, for most sampled taxa, fallows harbour the most distinct species assemblages, while that of other management regimes are largely overlapping. Management has the largest effect on species composition, whereas environmental parameters are of minor importance. Long-term grassland fallows seem to be highly valuable for arthropod conservation, even in a landscape with a low overall land-use intensity, providing structural heterogeneity. In conclusion, such fallows should be subsidized agri-environmental schemes, to preserve insect and spider diversity.
Cultural eutrophication due to excessive inputs of nutrients seriously threatens aquatic ecosystems worldwide and is one of the major anthropogenic stressors on aquatic biota in European rivers. In streams and shallow rivers, its effects include excessive periphyton growth, which causes biological clogging and thereby oxygen depletion in the hyporheic zone. The result is a serious degradation of habitat quality for benthic invertebrates as well as for the eggs and larvae of gravel-spawning fish. Unlike in standing waters, efficient tools for controlling eutrophication in rivers are lacking. However, top-down control of the food-web by manipulating fish stocks, similar to the biomanipulation successfully applied in lakes, offers a promising approach to mitigating the effects of eutrophication in shallow rivers, especially those in which major reductions in nutrient inputs are not feasible. The overall aim of this thesis was to assess the potential for top-down control by two large cypriniform fish, the common nase (Chondrostoma nasus), the only obligate herbivorous fish species in European rivers, and the omnivorous European chub (Squalius cephalus), to mitigate the effects of eutrophication in medium-sized rivers. I therefore conducted field experiments on different spatial and temporal scales in the hyporhithral zone of a eutrophic gravel-bed river. Generally, the results of those experiments revealed the crucial role of fish-mediated top-down effects in river food webs. In a 4-year reach-scale experiment, the key contribution of my thesis, the enhancement of fish densities significantly increased both oxygen availability and water exchange in the upper layer of the hyporheic zone, even though the top-down effects of the fish on periphyton biomass were relatively small. These findings were supported by those of a 4-week mesocosm experiment, which also provided insights into the mechanisms underlying the mitigation of eutrophication effects by nase and chub. The top-down effects of both fish species reduced hyporheic oxygen depletion, suggesting a reduction of biological clogging. The positive effects of herbivorous nase on hyporheic oxygen availability could be attributed to benthic grazing, whereas the reduction of hyporheic oxygen depletion in the presence of omnivorous chub was best explained by the enhanced bioturbation induced by the fish’s benthic foraging. Overall, the results of my thesis demonstrate that biomanipulation achieved by enhancing herbivorous and omnivorous fish stocks can mitigate the effects of eutrophication in medium-sized European rivers. The results may be the first step towards the establishment of biomanipulation as a supportive management tool for eutrophication control in running waters and therefore as a strategy to preserve aquatic biodiversity.
Nandi forests (South and North Nandi forests) are situated in the Rift Valley Province of Kenya very close to Kakamega forest. From previous documents it has been seen that Kakamega and Nandi forests were connected to each other forming one big "U" shaped forest block till the beginnings of 1900s. Due to human pressures, currently there are three different forests form the previous one block forest. Although they were one forest, information on Nandi forests is very scanty when it is compared to that of Kakamega forest. The species composition and diversity as well as plant communities and population structure of Nandi forests have not been studied. Information is not available about the similarity status of South and North Nandi forests. Furthermore the natural regeneration potential (seedling bank) of these forests is not well studied and documented. Hence this study aims to fill these gaps.
In this study totally 76 quadrates (49 from South Nandi and 27 from North Nandi) were used to collect data. In the South Nandi forests 27 of the quadrates were laid in the better side of the forest (at Kobujoi) and the remaining 22 were in the heavily disturbed part of this forest (Bonjoge). The quadrates were arranged on transects that have one to one and half km which were parallel to the slope. The distance between the quadrates was 100 meter and transects are 500 m apart. The size of the main quadrate was 400 m2 (20 X 20 m) which also had five small plots (3 X 3 m) distributed on the four corners and in the center. Each woody plants (climbers, shrubs and trees) having more than one meter and greater than two centimeter diameter at breast height (dbh) were measured and recorded. Seedlings and herbaceous plants were sampled in the smaller plots. Individual plants were identified at species level and when it was not possible to identify in the field voucher specimen were prepared and latter identified at the East African Herbarium, National Museum of Kenya, and Nairobi. Clustering and ordination were performed using PC-ORD and CANOCO ecological softwares, respectively. For both clustering and ordination abundance data of the species was used. Shannon diversity index and evenness were computed using PC-ORD while similarity indices, Fisher alpha, rarefaction, species richness estimation (nonparametric species richness estimators) were conducted using EstimateS. Indicator species analysis was undertaken using PC-ORD. Basal area and height class distribution at forests level or site level (Bonjoge and Kobujoi) and diameter (dbh) class distribution for selected trees species were performed to evaluate population structure.
Furthermore importance value (IV) of woody plant species was calculated. SPSS version 16 was used to undertake both parametric (when data assume normal distribution) and nonparametric (when data are not assuming normal distribution) comparison of means, correlation and regression analysis.
In this study totally 321 vascular plant species comprising 92 families and 243 genera were identified in Nandi forests (both South and North Nandi forests). In South Nandi forest 253 plant species form 82 families and 201 genera were recorded while in North Nandi 181 species comprising 67 families and 155 genera were recorded. Jackknife second order estimators gave the highest species richness estimate for both South and North Nandi forests i.e. 284 and 209, respectively. In the case of highly disturbed and less disturbed parts of South Nandi forest 138 and 172 vascular plant species were recorded, respectively. Asteraceae, Rubiaceae and Euphorbiaceae are the top three species rich families of Nandi forests. In terms of different diversity measures (i.e. alpha and beta diversity, Fisher alpha, Shannon diversity and evenness indices) South Nandi is more diverse than North Nandi forest. Sörensen and Jaccard (classic) as well as their respective abundance based similarities showed that there is a low species similarity between South and Nandi forests. The cluster analysis resulted in three different plant communities and this result is supported by the ordination result.
South and North Nandi forest has inverted "J" height class distribution showing that larger proportion of woody plant individuals are found in the lower height classes. Similar pattern is observed when the diameters of all woody plants were considered together. However, different diameter class distributions (seven types) were identified when selected tree species were analyzed separately. It has been observed that the basal area of South Nandi forest is significantly lower than that of North Nandi forest (Mann-Whitney U =358, p < 0.001). Similarly Bonjoge has significantly lower basal area (t-value=3.77, p<0.01) than that of Kobujoi. Number of woody plat seedlings in South Nandi forest is significantly higher than that of North Nandi (Mann-Whitney U = 362.5, p<0.001). In the same way Bonjoge has significantly smaller number of ssedlings than Kobujoi (t-value 4.24, p<0.001). Most of species in both forests are able to resprout from stumps after physical damage; hence this helps the regeneration of the forests in addition to seedling banks. This study enables to fill some of the information gaps about Nandi forests especially of floristic composition, population structure, natural regeneration and human impacts on this ecosystem.
Because silver nanoparticles (Ag NPs) are broadly applied in consumer products, their leaching will result in the continuous release of Ag NPs into the natural aquatic environment. Therefore, bacterial biofilms, as the prominent life form of microorganisms in the aquatic environment, are most likely confronted with Ag NPs as a pollutant stressor. Notwithstanding the significant ecological relevance of bacterial biofilms in aquatic systems, and though Ag NPs are expected to accumulate within these biofilms in the environment, the knowledge on the environmental and ecological impact of Ag NPs, is still lagging behind the industrial growth of nanotechnology. Consequently, aim of this thesis was to perform effect assessment of Ag NP exposure on bacterial biofilms with ambient Ag NPs concentrations and under environmentally relevant conditions. Therefore, a comprehensive set of methods was applied in this work to study if and how Ag NPs of two different sizes (30 and 70 nm) affect bacterial biofilms i.e. both monospecies biofilms and freshwater biofilms in environmentally relevant concentrations (600 - 2400 µg l-1). Within the first part of this work, a newly developed assay to test the mechanical stability of
monospecies biofilms of the freshwater model bacterium Aquabacterium citratiphilum was validated. In the first study, to investigate the impact of Ag NPs on the mechanical stability of bacterial biofilms, sublethal effects on the mechanical stability of the biofilms were observed with negative implications for biostabilization. Furthermore, as it is still challenging to monitor the ecotoxicity of Ag NPs in natural freshwater environments, a mesocosm study was performed in this work to provide the possibility for the detailed investigation of effects of Ag NPs on freshwater biofilms under realistic environmental conditions. By applying several approaches to analyze biofilms as a whole in response to Ag NP treatment, insights into the resilience of bacterial freshwater biofilms were obtained. However, as revealed by t-RFLP fingerprinting combined with phylogenetic studies based on the 16S gene, a shift in the bacterial community composition, where Ag NP-sensitive bacteria were replaced by more Ag NP-tolerant species with enhanced adaptability towards Ag NP stress was determined. This shift within the bacterial community may be associated with potential detrimental effects on the functioning of these biofilms with respect to nutrient loads, transformation and/or degradation of pollutants, and biostabilization. Overall, bringing together the key findings of this thesis, 4 general effect mechanisms of Ag NP treatment have been identified, which can be extrapolated to natural freshwater biofilms i.e. (i) the identification of Comamonadaceae as Ag NP-tolerant, (ii) a particular resilient behaviour of the biofilms, (iii) the two applied size fractions of Ag NPs exhibited similar effects independent of their sizes and their synthesis method, and (iv) bacterial biofilms show a high uptake capacity for Ag NPs, which indicates cumulative enrichment.
Ecological assessment approaches based on benthic invertebrates in Euphrates tributaries in Turkey
(2019)
Sustainable water management requires methods for assessing ecological stream quality. Many years of limnological research are needed to provide a basis for developing such methods. However, research of this kind is still lacking in Turkey. Therefore, the aim of this doctoral thesis was to provide basic research in the field of aquatic ecology and to present methods for the assessment of ecological stream quality based on benthic invertebrates. For this purpose, I selected 17 tributaries of the Euphrates with a similar typology/water order and varying levels of pollution or not affected by pollution at all. The characterisation of the natural mountain streams was the first important step in the analysis of ecological quality. Based on community indices, I found that the five selected streams had a very good ecological status. I also compared the different biological indications, collected on two occasions ¬– once in spring (May) and once in autumn (September) – to determine the optimal sampling time. The macroinvertebrate composition differed considerably between the two seasons, with the number of taxa and Shannon index being significantly higher in autumn than in spring. In the final step, I examined the basal resources of the macroinvertebrates in the reference streams with an isotope analysis. I found that FPOM and biofilm were the most relevant basal resources of benthic invertebrates. Subsequently, based on the similarity of their community structures, I divided the 17 streams into three quality classes, supported by four community indices (EPT [%], EPTCBO [%], number of individuals, evenness). In this process, 23 taxa were identified as indicators for the three quality classes. In the next step, I presented two new or adapted indices for the assessment of quality class. Firstly, I adapted the Hindu Kush-Himalaya biotic index to the catchment area of the Euphrates and created a new, ecoregion-specific score list (Euph-Scores) for 93 taxa. The weighted ASPT values, which were renamed the Euphrates Biotic Score (EUPHbios) in this study, showed sharper differentiations of quality classes compared to the other considered ASPT values. Thus, this modified index has proved to be very effective and easy to implement in practical applications. As a second biological index, I suggested the proportion of habitat specialists. To calculate this index, the habitat preferences of the 20 most common benthic invertebrates were identified using the new habitat score. The proportion of habitat specialists differed significantly among the three quality classes with higher values in natural streams than in polluted streams. The methods and results presented in this doctoral thesis can be used in a multi-metric index for a Turkish assessment programme.
Amphibian populations are declining worldwide for multiple reasons such as habitat destruction and climate change. An example for an endangered European amphibian is the yellow-bellied toad Bombina variegata. Populations have been declining for decades, particularly at the northern and western range margin. One of the extant northern range centres is the Westerwald region in Rhineland-Palatinate, Germany. To implement informed conservation activities on this threatened species, knowledge of its life-history strategy is crucial. This study therefore focused on different developmental stages to test predictions of life-history theory. It addressed (1) developmental, (2) demographic and (3) genetic issues of Bombina variegata as a model organism: (1) Carry-over effects from larval environment to terrestrial stages and associated vulnerability to predators were investigated using mesocosm approaches, fitness tests and predation trials. (2) The dynamics and demography of B. variegata populations were studied applying a capture-mark-recapture analysis and skeletochronology. The study was complemented through (3) an analysis of genetic diversity and structuring of B. variegata populations using 10 microsatellite loci. In order to reveal general patterns and characteristics among B. variegata populations, the study focused on three geographical scales: local (i.e. a former military training area), regional (i.e. the Westerwald region) and continental scale (i.e. the geographical range of B. variegata). The study revealed carry-over effects of larval environment on metamorph phenotype and behaviour causing variation in fitness in the early terrestrial stage of B. variegata. Metamorph size and condition are crucial factors for survival, as small-sized individuals were particularly prone to predator attacks. Yellow-bellied toads show a remarkable fast-slow continuum of the life-history trait longevity. A populations’ position within this continuum may be determined by local environmental stochasticity, i.e. an extrinsic source of variation, and the efficiency of chemical antipredator protection, i.e. an intrinsic source of variation. Extreme longevity seems to be an exception in B. variegata. Senescence was absent in this study. Weather variability affected reproductive success and thus population dynamics. The dispersal potential was low and short-term fragmentation of populations caused significant genetic differentiation at the local scale. Long-term isolation resulted in increased genetic distance at the regional scale. At the continental scale, populations inhabiting the marginal regions were deeply structured with reduced allelic richness. As consequence of environmental changes, short-lived and isolated B. variegata populations at the range margin may face an increased risk of extinction. Conservation measures should thus improve the connectivity among local populations and reinforce annual reproductive success. Further research on the intraspecific variation in B. variegata skin toxins is required to reveal potential effects on palatability and thus longevity.