Revisiting the species list of freshwater fish in Israel based on DNA barcoding.

Israel's region forms a continental bridge; hence, the freshwater fish fauna in Israel consists of unique populations of species that originated from Africa, Asia, or Europe and are often endemic or at the edge of their distribution range. Worldwide, fish biodiversity suffers significantly from pressures and disturbances of freshwater habitats, especially in arid regions, such as in parts of Israel. Biodiversity conservation requires efficient tools for monitoring changes in populations. DNA barcoding, by complementing and enhancing species identification, provides such monitoring tools. In this study, over 200 specimens representing over 28 species were DNA barcoded and together with previously available records, a DNA barcoding database for freshwater fish of Israel was established. Of the 71 distinct barcodes generated, 37% were new, attesting to the uniqueness of fish populations in Israel. For most species, morphological and molecular species identifications agreed. However, discrepancies were found for five genera. Based on DNA barcoding, we propose Acanthobrama telavivensis as a junior synonym for Acanthobrama lissneri. In Garra spp., we propose splitting Garra nana into two species and assigning Garra rufa in the region to Garra jordanica, or possibly to two species. Israeli Pseudophoxinus kervillei is not the same species as in Syria and Lebanon. However, Pseudophoxinus syriacus might not be endangered since it is genetically very similar to Pseudophoxinus drusensis. In Israel, instead of five reported Oxynoemacheilus species, combining DNA barcoding with morphology suggests only three. Genetic and geographic separation suggested that Aphanius mento is likely a species complex. The study provides a thorough barcoding database, suggests significant species reconsiderations in the region, and highlights the Sea of Galilee and the Beit She'an valley streams as biodiversity "hotspots." This study will therefore promote further studying of the fish species in the region and their ecology, as well as the monitoring and conservation of freshwater fish biodiversity in Israel and the region.

To Be, or Not to Be: That Is the Hamletic Question of Cryptic Evolution in the Eastern Atlantic and Mediterranean Raja miraletus Species Complex.

Despite a high species diversity, skates (Rajiformes) exhibit remarkably conservative morphology and ecology. Limited trait variations occur within and between species, and cryptic species have been reported among sister and non-sister taxa, suggesting that species complexes may be subject to stabilising selection. Three sibling species are currently recognised in the Raja miraletus complex: (i) R. miraletus occurring along the Portuguese and Mediterranean coasts, (ii) R. parva in the Central-Eastern Atlantic off West Africa and (iii) R. ocellifera in the Western Indian Ocean off South Africa. In the present study, the genetic variation at mitochondrial and nuclear markers was estimated in the species complex by analysing 323 individuals sampled across most of its geographical distribution area to test the hypothesis that restricted gene flow and genetic divergence within species reflect known climate and bio-oceanographic discontinuities. Our results support previous morphological studies and confirm the known taxonomic boundaries of the three recognised species. In addition, we identified multiple weakly differentiated clades in the Northeastern Atlantic Ocean and Mediterranean, at least two additional cryptic taxa off Senegal and Angola, a pronounced differentiation of ancient South African clades. The hidden genetic structure presented here may represent a valuable support to species' conservation action plans.

Freshwater fishes of Israel; a revised and updated annotated checklist2023.

The current status of the freshwater fishes of Israel is revised, and an updated checklist is presented. The confirmed freshwater fishes of Israel comprise 55 species belonging to nine orders, 14 families, and 39 genera. Among these, 19 species (34.6%) are alien, and four species (7.3%) are considered endemic to Israel. The orders with the largest numbers of species in the ichthyofauna of Israel are Cypriniformes (19 species), followed by Cichliformes (14 species), Cyprinodontiformes (seven species), Mugiliformes (six species), Siluriformes (four species), Salmoniformes (two species), and the others represent one species in each. At the family level, the Cichlidae have the greatest number of species (14 species; 25.5% of the total species), followed by Cyprinidae (10 species), Leuciscidae and Mugilidae (six species in each), Aphaniidae (four species), Nemacheilidae and Poecilidae (three species in each). According to IUCN Red List criteria, among 36 naturally distributed species (alien species not included), two species are extinct (EX) and nine species (25.0%) are categorized as threatened extinctions, with two (5.6%) CR, four (11.1%) EN, and three (8.3%) VU.

Establishing and using a genetic database for resolving identification of fish species in the Sea of Galilee, Israel.

Freshwaters are a very valuable resource in arid areas, such as Mediterranean countries. Freshwater systems are vulnerable ecological habitats, significantly disturbed globally and especially in arid areas. The Sea of Galilee is the largest surface freshwater body in the Middle East. It is an isolated habitat supporting unique fish populations, including endemic species and populations on the edge of their distribution range. Using the Sea of Galilee for water supply, fishing and recreation has been placing pressure on these fish populations. Therefore, efficient monitoring and effective actions can make a difference in the conservation of these unique fish populations. To set a baseline and develop molecular tools to do so, in this study, DNA barcoding was used to establish a database of molecular species identification based on sequences of Cytochrome C Oxidase subunit I gene. DNA barcodes for 22 species were obtained and deposited in Barcode of Life Database. Among these, 12 barcodes for 10 species were new to the database and different from those already there. Barcode sequences were queried against the database and similar barcodes from the same and closely related species were obtained. Disagreements between morphological and molecular species identification were identified for five species, which were further studied by phylogenetic and genetic distances analyses. These analyses suggested the Sea of Galilee contained hybrid fish of some species and other species for which the species definition should be reconsidered. Notably, the cyprinid fish defined as Garra rufa, should be considered as Garra jordanica. Taken together, along with data supporting reconsideration of species definition, this study sets the basis for further using molecular tools for monitoring fish populations, understanding their ecology, and effectively managing their conservation in this unique and important habitat and in the region.

Planiliza lauvergnii (Eydoux & Souleyet, 1850), a senior synonym of Planiliza affinis (Günther, 1861) with a re-evaluation of keeled back mullets (Mugiliformes: Mugilidae).

The taxonomic status of the keeled back mullets (Teleostei: Mugilidae) has been reinvestigated. Two nominal mugilid species having keeled backs from East Asia: Mugil lauvergnii Eydoux & Souleyet, 1850 and Mugil affinis Günther, 1861 have been re-evaluated through examination of the holotypes and fresh specimens. Comparison of morpho-meristic characters of the holotypes shows that both species are identical. Phylogenetic analysis based on mitochondrial cytochrome c oxidase 1 (CO1) confirmed morphological data by highlighting presence of a single clade from East Asia. Mugil lauvergnii (=Planiliza lauvergnii) is thus the sole keeled back mullet from East Asia and a senior synonym of Mugil affinis (=Planiliza affinis). The taxonomic status of two other keeled back mullets, Planiliza carinata and P. klunzingeri, is also contentious due to their similar morphology. Meristic and morphometric variation as well as sequence divergence between the two species are limited but phylogenetic analyses delineate well-supported clades consistent with biogeography and currently accepted taxonomy. Planiliza carinata and P. klunzingeri share a recent common ancestor in a Maximum Likelihood tree, with separate distribution ranges while P. lauvergnii formed a paraphyletic lineage. Based on present findings, we suggest maintenance of the taxonomic distinction of P. klunzingeri and P. carinata and discuss its evolutionary significance.

Genome Analysis of Lagocephalus sceleratus: Unraveling the Genomic Landscape of a Successful Invader.

The Tetraodontidae family encompasses several species which attract scientific interest in terms of their ecology and evolution. The silver-cheeked toadfish (Lagocephalus sceleratus) is a well-known "invasive sprinter" that has invaded and spread, in less than a decade, throughout the Eastern and part of the Western Mediterranean Sea from the Red Sea through the Suez Canal. In this study, we built and analysed the first near-chromosome level genome assembly of L. sceleratus and explored its evolutionary landscape. Through a phylogenomic analysis, we positioned L. sceleratus closer to T. nigroviridis, compared to other members of the family, while gene family evolution analysis revealed that genes associated with the immune response have experienced rapid expansion, providing a genetic basis for studying how L. sceleratus is able to achieve highly successful colonisation. Moreover, we found that voltage-gated sodium channel (NaV 1.4) mutations previously connected to tetrodotoxin resistance in other pufferfishes are not found in L. sceleratus, highlighting the complex evolution of this trait. The high-quality genome assembly built here is expected to set the ground for future studies on the species biology.

An updated Checklist of the Mediterranean fishes of Israel, with illustrations of recently recorded species and delineation of Lessepsian migrants.

This checklist of the Mediterranean fishes of Israel enumerates 469 species which is an addition of 62 species since the previous checklist of 2005. This new checklist includes 58 Condrichthys and 411 Osteicthys species. Most newly-recorded species are of Red Sea origin (Lessepsian migrants)-38 species, 25 species are from previously poorly investigated habitats, mainly deep water, while two species reached the Mediterranean most likely by ballast water and two are aquaculture escapees.                The dramatic increase in the number of Lessepsian migrants (an average of 2.5 species per year) is most likely due to the increased water influx between the Red Sea and the Mediterranean, following the recent opening of the new parallel, 72 km, "new canal" and the enlargement of other parts of the Suez Canal.

A new species of Lestrolepis from the Red Sea, with redescription of Lestrolepis pofi (Harry, 1953) (Aulopiformes: Parelepididae).

A new species of the genus Lestrolepis is described based on 6 specimens collected from the Red Sea. The species differs from the congeners in having 31‒34 anal-fin rays, 63‒65 total lateral-line scales, 28‒30 prehaemal vertebrae and 79‒81 total vertebrae. Lestidium pofi Harry, previously recognized as a junior synonym of "Lestrolepis" luetkeni (Ege), is recognized as a valid species of Lestrolepis. A redescription of pofi is provided, based on specimens collected from off Hawaii, Japan, Madagascar and Australia.

Constructing the genetic population demography of the invasive lionfish Pterois miles in the Levant Basin, Eastern Mediterranean.

The recent invasion of the lionfish Pterois miles to the Mediterranean draws major concerns to the fate of the indigenous ecosystem, based on previous knowledge of the species' detrimental capabilities as an introduced species in the Western Atlantic Ocean. In order to determine invasive patterns in the Eastern Mediterranean, we compared the genetic divergence of two mtDNA markers, the COI and D-loop, between and within the introduced Levantine and native range Red Sea populations of the lionfish. COI region presented a remarkably shallow genealogy, and both genes have failed to show a definite geographic population structure, with non-significant AMOVA and low pairwise FST values. A shared haplotype across all localities in the D-loop provided probable confirmation for the Red Sea origin of the invasive population, and a number of introduced haplotypes indicated that the Mediterranean populations are a product of multiple invasion events. Finally, we observed large haplotype diversity in the Red Sea samples that were absent from the introduced localities, implying a possible future enforcement to the invasive genetic pool in the Mediterranean Sea.

Checklist of the Red Sea Fishes with delineation of the Gulf of Suez, Gulf of Aqaba, endemism and Lessepsian migrants.

The current checklist provides for each species of the Red Sea its records in the Gulf of Suez, Gulf of Aqaba, Red Sea main basin and its general distribution.This new checklist of Red Sea fishes enumerates 1207 species, representing 164 families. Of these, 797 species were recorded from the Gulf of Aqaba and 339 from the Gulf of Suez. The number of species from the Gulf of Suez is evidently lower than the actual number not including 27 Lessepsian (Red Sea) migrants to the Mediterranean that most likely occur in the Gulf. The current list includes 73 species that were newly described for science since the last checklist of 2010. The most specious Osteichthyes families are: Gobiidae (134 species), Labridae (66), Apogonidae (59), Serranidae (including Anthiadinae) (44), Blenniidae (42), Carangidae (38), Muraenidae (36), Pomacentridae (35), Syngnathidae (34), Scorpaenidae (24) and Lutjanidae (23). Among the families of Chondrichthyes, the most specious families are the Carcharhinidae (18 species) and Dasyatidae (11). The total number of endemic species in the Red Sea is 174 species, of these, 34 species are endemic to the Gulf of Aqaba and 8 to the Gulf of Suez.

Natural history and molecular evolution of demersal Mediterranean sharks and skates inferred by comparative phylogeographic and demographic analyses.

BACKGROUND: The unique and complex paleoclimatic and paleogeographic events which affected the Mediterranean Sea since late Miocene deeply influenced the distribution and evolution of marine organisms and shaped their genetic structure. Following the Messinian salinity crisis and the sea-level fluctuations during the Pleistocene, several Mediterranean marine species developed deep genetic differentiation, and some underwent rapid radiation. Here, we consider two of the most prioritized groups for conservation in the light of their evolutionary history: sharks and rays (elasmobranchs). This paper deals with a comparative multispecies analysis of phylogeographic structure and historical demography in two pairs of sympatric, phylogenetically- and ecologically-related elasmobranchs, two scyliorhinid catsharks (Galeus melastomus, Scyliorhinus canicula) and two rajid skates (Raja clavata, Raja miraletus). Sampling and experimental analyses were designed to primarily test if the Sicilian Channel can be considered as effective eco-physiological barrier for Mediterranean demersal sympatric elasmobranchs. METHODS: The phylogeography and the historical demography of target species were inferred by analysing the nucleotide variation of three mitochondrial DNA markers (i.e., partial sequence of COI, NADH2 and CR) obtained from a total of 248 individuals sampled in the Western and Eastern Mediterranean Sea as well as in the adjacent northeastern Atlantic Ocean. Phylogeographic analysis was performed by haplotype networking and testing spatial genetic differentiation of samples (i.e., analysis of molecular variance and of principal components). Demographic history of Mediterranean populations was reconstructed using mismatch distribution and Bayesian Skyline Plot analyses. RESULTS: No spatial genetic differentiation was identified in either catshark species, while phylogeographic structure of lineages was identified in both skates, with R. miraletus more structured than R. clavata. However, such structuring of skate lineages was not consistent with the separation between Western and Eastern Mediterranean. Sudden demographic expansions occurred synchronously during the upper Pleistocene (40,000-60,000 years ago) in both skates and G. melastomus, likely related to optimal environmental conditions. In contrast, S. canicula experienced a slow and constant increase in population size over the last 350,000 years. DISCUSSION: The comparative analysis of phylogeographic and historical demographic patterns for the Mediterranean populations of these elasmobranchs reveals that historical phylogeographic breaks have not had a large impact on their microevolution. We hypothesize that interactions between environmental and ecological/physiological traits may have been the driving force in the microevolution of these demersal elasmobranch species in the Mediterranean rather than oceanographic barriers.

Dysomma alticorpus, a new species of cutthroat eel from the Gulf of Aqaba, Red Sea (Teleostei: Synaphobranchidae).

The cutthroat eel Dysomma alticorpus n. sp. is described based on a single specimen collected in a trammel net at a depth of 350m off Eilat, Israel, Gulf of Aqaba, Red Sea. The new species belongs to the Dysomma anguillare species complex, which comprises species possessing a well-developed pectoral fin, intermaxillary teeth, a uniserial row of 7-15 large compound teeth in the lower jaw (which may be followed by a few smaller teeth), and an anteriorly situated anus with the trunk shorter than the head length. It is characterised by a combination of the following characters: origin of the dorsal fin well anterior to the base of the pectoral fin, predorsal length 13.8% TL; preanal length 22.8% TL; three compound teeth on the vomer; head pores: IO 4, SO 3; M 6; POP 0; AD 1, F 0, ST 0; lateral-line pores: predorsal 4, prepectoral 8, preanal 14, total 57-58, the last at the posterior two-thirds of the total length; MVF 7-16-115; total vertebrae 115. Dysomma alticorpus n. sp. is compared with other species of the genus. A revised key to the species of the genera Dysomma and Dysommina is provided.

The clinical effects of the venomous Lessepsian migrant fish Plotosus lineatus (Thunberg, 1787) in the Southeastern Mediterranean Sea.

CONTEXT: Plotosus lineatus is a venomous fish that has migrated from the Indo-Pacific region to the Mediterranean Sea (Lessepsian migrant). Its presence in the Mediterranean Sea was first recorded in 2002 and was observed in growing schools. Its spines contain toxins with lytic, hemolytic and edematous activities. OBJECTIVE: To characterize the injuries caused by Plotosus lineatus in the Southeastern Mediterranean Sea. METHODS: A prospective observational case series of consultations provided by a national Poison Center pertaining to Plotosus lineatus from 2007 to 2016. Demographic and clinical data and method of fish identification were retrieved from the medical toxicological records, and described. RESULTS: Eighty four cases were included; the main findings are: median age 35 (range 3-80) years, 91.7% males, 51.2% fishermen, 78.6% palm injuries, 94% and 4.8% were mildly and moderately injured, respectively. Main local manifestations included pain, puncture wound, swelling, and erythema (90.5%, 70.2%, 33.3%, and 16.7%, respectively). Systemic signs were minor and infrequent (≤7.1%), including hypertension, tachycardia, vomiting, chills, and weakness. Management included wound disinfection, immersion in hot water, tetanus prophylaxis, and analgesics. No patient required hospital admission. The fish was identified mostly by the victim with the aid of the Poison Center (mainly by typical description, and a picture), and some by marine biologists. CONCLUSIONS: Plotosus lineatus is a new fish in the Southeastern Mediterranean Sea. It affects fishermen handling fishing nets, and beach hikers stepping on or holding it. Injuries caused by its spines usually result in minor effects; pain may be intense. Treatment includes disinfection, analgesics, and antitetanus and antibiotics as needed. No lethal cases were recorded, unlike exposure of animals to the venom of the Indo-Pacific species; reason is unclear. Our series illustrates the consequences of manmade disruption of ecosystem resulting in invasion of toxic species to a new environment, affecting human health.

Improving the Conservation of Mediterranean Chondrichthyans: The ELASMOMED DNA Barcode Reference Library.

Cartilaginous fish are particularly vulnerable to anthropogenic stressors and environmental change because of their K-selected reproductive strategy. Accurate data from scientific surveys and landings are essential to assess conservation status and to develop robust protection and management plans. Currently available data are often incomplete or incorrect as a result of inaccurate species identifications, due to a high level of morphological stasis, especially among closely related taxa. Moreover, several diagnostic characters clearly visible in adult specimens are less evident in juveniles. Here we present results generated by the ELASMOMED Consortium, a regional network aiming to sample and DNA-barcode the Mediterranean Chondrichthyans with the ultimate goal to provide a comprehensive DNA barcode reference library. This library will support and improve the molecular taxonomy of this group and the effectiveness of management and conservation measures. We successfully barcoded 882 individuals belonging to 42 species (17 sharks, 24 batoids and one chimaera), including four endemic and several threatened ones. Morphological misidentifications were found across most orders, further confirming the need for a comprehensive DNA barcoding library as a valuable tool for the reliable identification of specimens in support of taxonomist who are reviewing current identification keys. Despite low intraspecific variation among their barcode sequences and reduced samples size, five species showed preliminary evidence of phylogeographic structure. Overall, the ELASMOMED initiative further emphasizes the key role accurate DNA barcoding libraries play in establishing reliable diagnostic species specific features in otherwise taxonomically problematic groups for biodiversity management and conservation actions.

Mulloidichthys flavolineatus flavicaudus Fernandez-Silva & Randall (Perciformes, Mullidae), a new subspecies of goatfish from the Red Sea and Arabian Sea.

The number of goatfish species has increased recently, thanks in part to the application of molecular approaches to the taxonomy of a family with conservative morphology and widespread intraspecific color variation. A new subspecies Mulloidichthys flavolineatus flavicaudus Fernandez-Silva & Randall is described from the Red Sea and Arabian Sea, including Socotra and Gulf of Oman. It is characterized by a yellow caudal fin, 25-28 gill rakers, and 37-38 lateral-line scales and it is differentiated from nominal subspecies Mulloidichthys flavolineatus flavolineatus by 1.7% sequence divergence at the mitochondrial cytochrome b gene. The morphometric examination of specimens of Mulloidichthys flavolineatus flavolineatus revealed variation in head length, eye diameter, and barbel length, in western direction from the Hawaiian Islands, South Pacific, Micronesia, and the East Indies to the Indian Ocean. The population of Mulloidichthys flavolineatus flavicaudus subsp. n. in the Gulf of Aqaba differs from that of the remaining Red Sea by shorter barbels, smaller eyes, shorter head, and shorter pelvic fins. We present a list of 26 endemic fishes from the Gulf of Aqaba and discuss the probable basis for the endemism in the light of the geological history of this region.

Genomic signatures of rapid adaptive evolution in the bluespotted cornetfish, a Mediterranean Lessepsian invader.

Biological invasions are increasingly creating ecological and economical problems both on land and in aquatic environments. For over a century, the Mediterranean Sea has steadily been invaded by Indian Ocean/Red Sea species (called Lessepsian invaders) via the Suez Canal, with a current estimate of ~450 species. The bluespotted cornetfish, Fistularia commersonii, considered a 'Lessepsian sprinter', entered the Mediterranean in 2000 and by 2007 had spread through the entire basin from Israel to Spain. The situation is unique and interesting both because of its unprecedented rapidity and by the fact that it took this species c. 130 years to immigrate into the Mediterranean. Using genome scans, with restriction site-associated DNA (RAD) sequencing, we evaluated neutral and selected genomic regions for Mediterranean vs. Red Sea cornetfish individuals. We found that few fixed neutral changes were detectable among populations. However, almost half of the genes associated with the 47 outlier loci (potentially under selection) were related to disease resistance and osmoregulation. Due to the short time elapsed from the beginning of the invasion to our sampling, we interpret these changes as signatures of rapid adaptation that may be explained by several mechanisms including preadaptation and strong local selection. Such genomic regions are therefore good candidates to further study their role in invasion success.

Saurida lessepsianus a new species of lizardfish (Pisces: Synodontidae) from the Red Sea and Mediterranean Sea, with a key to Saurida species in the Red Sea.

Saurida lessepsianus n. sp., a lizardfish (Aulopiformes: Synodontidae) from the Red Sea and Mediterranean Sea, previously misidentified as S. undosquamis (Richardson) and more recently as S. macrolepis Tanaka, is described as a new species. It is characterised by the following combination of characters: dorsal fin with 11-12 rays; pectoral fins with 13-15 rays; lateral-line scales 47-51; transverse scale rows above lateral line 4½, below lateral line 5½; pectoral fins moderately long (extending to between just before or just beyond a line from origin of pelvic fins to origin of dorsal fin); 2 rows of teeth on outer palatines; 0-2 teeth on vomer; tongue with 3-6 rows of teeth posteriorly; caudal peduncle slightly compressed (depth a little more than width); upper margin of caudal fin with row of 3-8 (usually 6 or 7) small black spots; stomach pale grey to blackish anteriorly; intestine whitish. The species is common in the Red Sea and as a result of Lessepsian migration through the Suez Canal, it is now widely distributed in the eastern Mediterranean. The taxonomic status of two other Red Sea nominal species, Saurus badimottah Rüppell [= Saurida tumbil (Bloch)] and Saurida sinaitica Dollfus in Gruvel (a nomen nudum), is clarified. A key is provided for the species of Saurida in the Red Sea.

SEM study of the oral cavity of members of the Kyphosidae and Girellidae (Pisces, Teleostei), with remarks on Crenidens (Sparidae), focusing on teeth and taste bud numbers and distribution.

The present study compares dental morphology and taste bud distribution in the oral cavity of four species of the teleost family Kyphosidae, five species of Girellidae and one species of Sparidae. Some of these species are predominantly herbivorous, while others are omnivorous with a high portion of invertebrates in their diets. All the kyphosids feature one row of frontal cusped teeth on their jaws and areas of miniature teeth on the tongue and palate; the girellid species feature 2-5 rows of denticulate teeth, and no teeth inside the oral cavity. The total number of taste buds in the oral cavity is higher in Girella spp. than in the kyphosids, and their number is species-specific, not correlated with fish size. For example, Kyphosus bigibbus of 500mm standard length bears 1780 taste buds, while the kyphosid Neoscorpis lithophilus of 80mm bears 3460. The maximum number of taste buds, 7900, is found in Girella punctata of 60mm standard length, and the minimum number, 1320, in Kyphosus vaigiensis of 175mm. The higher number of taste buds appears to characterize species that possess a more diversified diet. The present study contributes to our understanding of the differences between the two families Kyphosidae and Girellidae. In particular, it relates the eco-morphological adaptations to the type of diet consumed by the various species.

Estimating the rate of biological introductions: Lessepsian fishes in the Mediterranean.

Sampling issues preclude the direct use of the discovery rate of exotic species as a robust estimate of their rate of introduction. Recently, a method was advanced that allows maximum-likelihood estimation of both the observational probability and the introduction rate from the discovery record. Here, we propose an alternative approach that utilizes the discovery record of native species to control for sampling effort. Implemented in a Bayesian framework using Markov chain Monte Carlo simulations, the approach provides estimates of the rate of introduction of the exotic species, and of additional parameters such as the size of the species pool from which they are drawn. We illustrate the approach using Red Sea fishes recorded in the eastern Mediterranean, after crossing the Suez Canal, and show that the two approaches may lead to different conclusions. The analytical framework is highly flexible and could provide a basis for easy modification to other systems for which first-sighting data on native and introduced species are available.