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Invasive species are classically thought to suffer from reduced within-population genetic variation compared to their native-range sources due to founder effects and population bottlenecks during introduction. Reduction in genetic variation in introduced species may limit population growth, increase the risk of extinction, and constrain adaptation, hindering the successful establishment and spread of an alien species. Results of recent empirical studies, however, show higher than expected genetic variation, rapid evolution, and multiple native-range sources in introduced populations, which challenge the classical scenario of invasive-species genetics. With mitochondrial DNA (mtDNA) sequence data, we examined the molecular genetics of 10 replicate introductions of 8 species of Anolis lizards. Eighty percent of introductions to Florida and the Dominican Republic were from multiple native-range source populations. MtDNA haplotypes restricted to different geographically distinct populations in the native range of a species commonly occurred as intrapopulation polymorphisms in introduced populations. Two-thirds of introduced populations had two or more sources, and admixture elevated genetic variation in half of the introduced populations above levels typical of native-range populations. The mean pairwise sequence divergence among haplotypes sampled within introduced populations was nearly twice that within native-range populations (2.6% vs. 1.4%). The dynamics of introductions from multiple sources and admixture explained the observed genetic contrasts between native and introduced Anolis populations better than the classical scenario for most introduced populations. Elevated genetic variation through admixture occurred regardless of the mode or circumstances of an introduction. Little insight into the number of sources or amount of genetic variation in introduced populations was gained by knowing the number of physical introductions, the size of a species' non-native range, or whether it was a deliberate or accidental introduction. We hypothesize that elevated genetic variation through admixture of multiple sources is more common in biological invasions than previously thought. We propose that introductions follow a sequential, two-step process involving a reduction in genetic variation due to founder effects and population bottlenecks followed by an increase in genetic variation if admixture of individuals from multiple native-range sources occurs.

Prioritizing conservation of source populations within landscapes is proposed as a strategy for recovering tigers globally. We studied population dynamics of tigers in Corbett National Park (CNP) in Indian Terai, which harbours the largest and highest density tiger population in any protected area of the world. Through population viability models, we demonstrate the importance of CNP in tiger recovery within western Terai. We camera trapped 521 km2 of CNP using open population capture–mark–recapture framework between 2010 and 2015 to estimate annual abundance, spatially explicit density, survival, recruitment, temporary movements, sex ratio and proportion of females breeding. We model metapopulation persistence with and without Corbett as a source within western Terai landscape at different levels of poaching and habitat connectivity. In 6 years, we recorded 6,202 photo‐captures of 307 individual tigers. Annual tiger abundance and density were stable at 120 (SE 19) and 14 (SE 3) per 100 km2 respectively. Detection probability of tigers was 0.18 (SE 0.03) and detection‐corrected male:female sex ratio was female biased (0.80 SE 0.13). Apparent annual survival probability was 0.79 (SE 0.05) for females and 0.60 (SE 0.04) for males. Survival of tigers in CNP (0.68 SE 0.12) was lower than that reported for other populations. CNP tigers showed high reproduction with 54.8 (SE 5.1)% females breeding and with addition of 35 (SE 8)% as new recruits to the population each year. Small tiger populations in western Terai with moderate poaching could only persist through dispersal from CNP. Synthesis and applications. Corbett tiger population was characterized by a stable high density, high reproductive rate and low survival, resulting in high turnover rates (32%–48%) between successive years. Such source populations could sustain low‐level poaching and with habitat connectivity, recover tiger populations across the landscape. This study establishes potential thresholds that can likely be achieved by tiger populations under optimal natural conditions and highlights the importance of prioritizing conservation of source populations within tiger landscapes. This information can be used to plan and implement realistic tiger recovery programmes globally. सार १) हमने भारतीय तराई भूभाग में स्तिथ कॉर्बेट राष्ट्रीय उद्यान में बाघों के जनांकिकी का अध्यन किया, जिसके माध्यम से बाघ संरक्षण की प्राथमिकता वाली महत्वपूर्ण बाघ आबादियों के लिए संभावित रणनीति का सुझाव दिया गया है I २) हमने छह वर्षों में ५२१ वर्ग कि०मी०. के छेत्र में रिमोट कैमरा ट्रैप के माध्यम से सैंपलिंग कर बाघों की आबादी और उनकी दीर्घ काल तक के जीवन क्षमता का अध्यन किया. हमने वैज्ञानिक “मार्क ‐रीकैप्चर “ मॉडल के माध्यम से बाघों की गड़ना, उनकी उतर जीवित, भर्ती दर, लिंगानुपात, प्रजनन धारी मादा का सालाना प्रतिशत आँका. इस सुचना से हमने पॉपुलेशन वायबिलिटी विश्लेषण (प० व० वी०)के मॉडल्स बनाये और बाघों की पश्चिम तराई भूभाग से विलुप्त होने की सम्भावना का आंकलन किया। हमने इन प० व० वी० मॉडल्स में अलग‐अलग सन्दर्भ, जैसे की अवैध शिकार एवम बाघों के वास स्थलों के बीच के गलियारों के जुड़ाव इत्यादी को रखकर बाघों की दीर्घावधि तक सतत रहने की सम्भावना को बताया I ३) हमने छह वर्षों,में कुल ६२०२ बाघों के छायाचित्रों का संग्रह किया, जिनके विश्लेषण उपरांत कुल ३०७ बाघ पाए गए I इन छह वर्षों में बाघों की जनसँख्या घनत्व (१४ ± ३ प्रति १०० सक. की. मि.) स्थिर पाया गया एवम लिंगानुपात (नर प्रति मादा) ०.८० ± ०.१३ मुख्य रूप से मादा प्रभावी रहा I नरों की उतर जीवित ६० % और मादा की ८० % पायी गयी. कॉर्बेट राष्ट्रीय उद्यान में बाघों की उच्च प्रजनन क्षमता पायी गयी, जहाँ सालाना कुल प्रजनन धरी मादा ५५% पायी गयीं एवम नए बाघों का भर्ती दर ३५% प्राप्त किया गया I ४) कॉर्बेट की जनसँख्या की विशेषता स्थिर उच्च घनत्व, उच्च प्रजनन दर और कम उतर जीवित और उच्च स्तरीय बदलाव(टर्न ओवर) (३२‐४८%) है I इस तरह की स्रोत आबादी छोटे स्तर पर अवैध शिकार को बर्दाश्त कर सकती है, और यदि बाघों के निवास स्थान के बीच के गलियारों को संरक्षित रखा जाए तो सम्पूर्ण भूभाग में बाघों की आबादी को पुनर्प्राप्त कर सकती है I हमारे इस अध्यन में उन सारे मापदंडों का विश्लेषण किया गया है जो प्राकृतिक परिस्थितियों में बाघ आबादी द्वारा प्राप्त किया जा सकता है I हमारा अध्यन इस स्रोत आबादी के संरक्षण को प्राथमिकता देने के महत्व पर प्रकाश डालता है I इस अध्यन से प्राप्त सूचना का प्रयोग विश्व सत्तर पर बाघों के पुनर्व्यास की योजना बनाने के लिए उपयोग किया जा सकता है I Corbett tiger population was characterized by a stable high density, high reproductive rate and low survival, resulting in high turnover rates (32%–48%) between successive years. Such source populations could sustain low‐level poaching and with habitat connectivity, recover tiger populations across the landscape. This study establishes potential thresholds that can likely be achieved by tiger populations under optimal natural conditions and highlights the importance of prioritizing conservation of source populations within tiger landscapes. This information can be used to plan and implement realistic tiger recovery programmes globally.

Previous studies evaluating the success of river restorations have rarely found any consistent effects on benthic invertebrate assemblages. In this study, we analyzed data from 24 river restoration projects in Germany dating back 1 to 12 years and 1231 data sets from adjacent river reaches that lie within 0-5, 5-10, and 10-15 km rings centered on the restored sites. We calculated restoration success and recolonization potential of adjacent river reaches based on stream-type-specific subsets of taxa indicative for good or bad habitat quality. On average, the restorations did not improve the benthic invertebrate community quality. However, we show that restoration success depends on the presence of source populations of desired taxa in the surrounding of restored sites. Only where source populations of additional desired taxa existed within a 0-5 km ring around the restored sites were benthic invertebrate assemblages improved by the restoration. Beyond the 5-km rings, this recolonization effect was no longer detected. We present here the first field results to support the debated argument that a lack of source populations in the areas surrounding restored sites may play an important role in the failure to establish desired invertebrate communities by the means of river restorations. In contrast, long-range dispersal of invertebrates seems to play a subordinate role in the recolonization of restored sites. However, because the surroundings of the restored sites were far from good ecological quality, the potential for improvement of restored sites was limited.

The existing literature on plant translocations focuses on post-translocation outcome while still overlooking issues related to the preparation phases. Yet, plant translocation programmes face significant pre-translocation challenges. In the present study, we want to share our pre-transplant experience on four rare plant species (Arnica montana, Campanula glomerata, Dianthus deltoides and Helichrysum arenarium), highlighting aspects we need to focus on while planning plant translocations. We emphasize some issues that need to be overcome before any translocation is undertaken during the four steps of translocation preparation, i.e. the selection and profiling of the target species, the seed collection, the development of propagation protocols and the assessment of plant fitness of the populations used as seed source. We discuss the implications of our results for designing translocation protocols. Our findings on A. montana show that if local seed sources are constrained to small remnant populations, seed quality may be poor. Preliminary tests using different kinds of growing medium provided valuable information for optimizing plant propagation protocols. Although it is attractive to establish propagation protocols using seeds obtained via Index Seminum (to avoid wasting collected source seeds), the results obtained were not always reproducible on the seeds collected in the wild source populations. Differences in pre-translocation plant fitness were also detected between seed source populations, which might reflect genetic diversity and maternal effects. As the translocated plants should capture as much genetic diversity as possible to ensure a high adaptive potential and improve establishment success, multisource reintroductions can be recommended.

Retracing the routes of invasions and determining the origins of invading species is often critical in understanding biological invasions. The Western conifer seed bug, Leptoglossus occidentalis, an insect native of western North America, was first accidentally introduced to eastern North America and then to Europe. The colonization of the entire European continent occurred in ca. 10–15 years, probably promoted by independent introductions in different parts of Europe. A multi-marker approach (mtDNA and microsatellites) combined with approximate Bayesian computation analyses was used to track the origin of European populations and to determine whether this rapid invasion was caused by multiple introductions. Our results show that at least two independent introductions of L. occidentalis have occurred in Europe. Moreover, the analyses showed a stronger genetic similarity of European invasive populations with the eastern North American populations than with those of the native range, suggesting that invasive North American population acted as a bridgehead for European invasion. The results also revealed that natural dispersal as well as human-mediated transportations as hitchhikers probably enhanced the rapid spread of this invasive pest across Europe. This study illustrates the complexity of a rapid invasion and confirms that bridgehead and multiple introductions have serious implications for the success of invasion.

Spatially explicit population models (SEPMs) are often considered the best way to predict and manage species distributions in spatially heterogeneous landscapes. However, they are computationally intensive and require extensive knowledge of species' biology and behavior, limiting their application in many cases. An alternative to SEPMs is graph theory, which has minimal data requirements and efficient algorithms. Although only recently introduced to landscape ecology, graph theory is well suited to ecological applications concerned with connectivity or movement. This paper compares the performance of graph theory to a SEPM in selecting important habitat patches for Wood Thrush (Hylocichla mustelina) conservation. We use both models to identify habitat patches that act as population sources and persistent patches and also use graph theory to identify patches that act as stepping stones for dispersal. Correlations of patch rankings were very high between the two models. In addition, graph theory offers the ability to identify patches that are very important to habitat connectivity and thus long-term population persistence across the landscape. We show that graph theory makes very similar predictions in most cases and in other cases offers insight not available from the SEPM, and we conclude that graph theory is a suitable and possibly preferable alternative to SEPMs for species conservation in heterogeneous landscapes.

Conservation translocation studies typically focus on assessing the fate of translocated individuals at recipient populations, and assessments of the source population's capacity to recover from removals are rare. Our understanding of the population level‐impacts of avian translocation remains limited because of the small sample sizes (i.e., number of territories) typically involved and because when breeding vacancies are refilled the identity of the colonizers is usually unknown. To address this information gap, we studied the impacts of translocating 13 territorial Florida scrub‐jay (Aphelocoma coerulescens) family groups (31 individuals) from long‐term study sites where most birds were color banded and of known age so the source of colonizers could be determined. Eleven of 13 (85%) vacated territories were colonized within 1–2 weeks and all family groups that occupied vacancies attempted reproduction in the year of the removal. Habitat quality appeared to affect reoccupancy for this early‐successional scrub specialist, as the two vacated territories that remained unoccupied were in the two oldest forest stands (14 years since mechanical clearing). In most cases (8 of 13; 62%), vacancies were partially, or entirely, absorbed into existing neighboring territories. However, two vacancies were colonized by newly formed family groups created by adults and helpers from other territories within the same management stand, and another vacancy was colonized by an immigrant group. This mix of refilling mechanisms for this species suggests a complex interplay of habitat quality, territoriality, and availability of non‐breeders on the landscape. Removing Florida scrub‐jay family groups from a source population may reduce the number of breeding territories if non‐breeding helpers are either unavailable in the landscape or unable to outcompete established neighboring territory holders for vacancies. More broadly, practitioners of avian translocation may benefit from considering habitat patch quality and the availability of non‐breeding adults when selecting birds for removal for translocation. Designing effective conservation translocations requires understanding the trade‐offs between negative impacts on source populations and positive impacts on recipient populations. This study found that most Florida scrub‐jay territories vacated by removals for translocation were quickly colonized before the subsequent breeding season, primarily through neighbor expansion. Translocation may reduce the size of a breeding population if non‐breeders are unavailable in the landscape or if they are unable to outcompete established neighboring territory holders.

Photosynthesis is a key biological process. However, we know little about whether plants change their photosynthetic strategy when introduced to a new range. We located the most likely source population for the South African beach daisy Arctotheca populifolia introduced to Australia in the 1930s, and ran a common-garden experiment measuring 10 physiological and morphological leaf traits associated with photosynthesis. Based on predictions from theory, and higher rainfall in the introduced range, we hypothesized that introduced plants would have a (i) higher photosynthetic rate, (ii) lower water-use efficiency (WUE) and (iii) higher nitrogen-use efficiency. However, we found that introduced A. populifolia had a lower photosynthetic rate, higher WUE and lower nitrogen-use efficiency than did plants from Arniston, South Africa. Subsequent site visits suggested that plants in Arniston may be able to access moisture on a rocky shelf, while introduced plants grow on sandy beaches where water can quickly dissipate. Our unexpected findings highlight that: (1) it is important to compare introduced species to their source population for an accurate assessment of evolutionary change; (2) rainfall is not always a suitable proxy for water availability and (3) introduced species often undergo evolutionary changes, but without detailed ecological information we may not be able to accurately predict the direction of these changes.

The critically endangered species Patella ferruginea (Gastropoda, Patellidae), endemic to the western Mediterranean, has breeding populations in both natural and artificial habitats, the latter of which are generally linked to port infrastructures. Over the past decade, the temporal change of this species’ population has been monitored (structure and density) using exhaustive censuses along Ceuta’s coast (Strait of Gibraltar), one of the few stronghold populations within the entire Mediterranean basin. This study focuses on the population dynamics of P. ferruginea in Ceuta and the environmental factors that affect the structure of this population, such as wave exposure, coastline heterogeneity, substratum roughness, substratum lithology, and chlorophyll-a concentration. Different potential negative interactions were also considered: angling, shell fishing, bathing in the intertidal, bathing near the intertidal, recreational boating and temporary migrant campsites nearby. The results have shown in the period 2011-2021, the estimated size of P. ferruginea population has increased by 200 %, from 55,902 to 168,463 individuals (of which 131,776 are adults). The subpopulation with the greatest increase in these years was the one settled on dolomitic rip-raps inside the Ceuta’s harbor, with an increase of 1,288%. The results of the present study indicate that Ceuta hosts the main population of this endangered species through its distributional range (Western Mediterranean), being a source population on the Southern Iberian Peninsula that its preservation must be prioritized. Statistical modelling has shown that the adult density of P. ferruginea is positively influenced by coastal heterogeneity, habitat area and substratum roughness, but negatively by vertical inclination, concentration of chlorophyll-a, and anthropogenic impact. These results also support the concept of ¨Artificial Marine Micro-Reserves¨ as a new area-based conservation measure according with the IUCN guidelines, as these will contribute to setting up a network of these source populations that promote genetic flow among populations, with eventual recolonization throughout its original distribution.

The literature suggests that small genomes promote invasion in plants, but little is known about the interaction of genome size with other traits or about the role of genome size during different phases of the invasion process. By intercontinental comparison of native and invasive populations of the common reed Phragmites australis, we revealed a distinct relationship between genome size and invasiveness at the intraspecific level. Monoploid genome size was the only significant variable that clearly separated the North American native plants from those of European origin. The mean Cx value (the amount of DNA in one chromosome set) for source European native populations was 0.490 ± 0.007 (mean ± SD), for North American invasive 0.506 ± 0.020, and for North American native 0.543 ± 0.021. Relative to native populations, the European populations that successfully invaded North America had a smaller genome that was associated with plant traits favoring invasiveness (long rhizomes, early emerging abundant shoots, resistance to aphid attack, and low C:N ratio). The knowledge that invasive populations within species can be identified based on genome size can be applied to screen potentially invasive populations of Phragmites in other parts of the world where they could grow in mixed stands with native plants, as well as to other plant species with intraspecific variation in invasion potential. Moreover, as small genomes are better equipped to respond to extreme environmental conditions such as drought, the mechanism reported here may represent an emerging driver for future invasions and range expansions.