Genetic Diversity in a Morphologically Conservative Invasive Taxon: Multiple Introductions of Swamp Eels to the Southeastern United States

Abstract

Genetic analysis of introduced populations, especially in morphologically conservative taxa, can clarify introduction histories, identify management units and source populations, provide a more realistic estimate of the frequency of successful invasion, and suggest strategies for preventing further introductions. In the last 7 years, populations of swamp eels, referred to the Asian genus Monopterus ( Family Synbranchidae) on the basis of external morphology, have been discovered in aquatic habitats near Atlanta, Georgia; Tampa, Florida; North Miami, Florida; and most recently in close proximity to Everglades National Park in Homestead, Florida. Swamp eels are large predators capable of dispersal over land and have the potential to disrupt already threatened ecosystems. We analyzed mitochondrial DNA sequences from four known populations in the continental United States and samples from Malaysia, Indonesia, Vietnam, and two locations in China to determine introduction histories, source populations, genetic diversity, and relationships among populations. Our results indicate that there have been at least three independent introductions of genetically distinct forms. Introduced populations in close proximity (separated by <40 km) are genetically distinct. The level of sequence difference among introduced populations reaches levels seen among sister families of teleost fishes for the same region of the mitochondrial genome. These genetically distinct introduced populations in all likelihood represent at least two and possibly three species. Regardless of species status, these genetically distinct lineages may be expected to vary in ecological or life‐history traits, representing different potential threats to the ecosystems where they have been introduced. Given the success of swamp eels in invading many habitats around the world, further study of these eels is warranted to elucidate the characteristics of successful invaders and invasions.

Morphological Characterization of Two Fresh Water Eels Monopterus cuchia (Hamilton, 1822) and Ophisternon bengalense (McClelland, 1844)

“…Among the Synbranchids, a few are known as a protogynous diandric fish (Nostro and Guerrero, 1996), with two different kinds of males. Collins et al (2002) reported that swamp eel have high fecundity and are protogynous hermaphrodite. In this experiment according to sexing pattern, there were nineteen males (59.4%), thirteen females (40.6%) in M. cuchia and five males (29.4%) and twelve females (70.6%) in O. bengalense.…”

Small but tough: What can ecophysiology of croaking gourami Trichopsis vittata (Cuvier, 1831) tell us about invasiveness of non-native fishes in Florida?

“…and bolster their ability to spread geographically. Other factors that could affect invasiveness include biotic resistance (e.g., Thompson et al 2012), specific requirements for egg/larval development or nesting, multiple introductions (Collins et al 2002), predation susceptibility (e.g., Rehage et al 2009) and propagule pressure (Colautti et al 2006). Application of modern modelling techniques may allow researchers to identify which variables are most important for an invader's success (and spread) and the critical thresholds for those variables (e.g.…”

Keragaman Morfometrik dan Genetik Gen COI Belut Sawah (Monopterus albus) Asal Empat Populasi di Jawa Barat

“…Informasi mengenai validasi identifikasi dengan BLASTn serta keragaman fenotipik (deskripsi atribut eksternal) yang dimiliki oleh ikan belut sawah asal Jawa Barat menggambarkan bahwa M. albus dikategorikan sebagai spesies komplek seperti yang diungkapan oleh beberapa peneliti sebelumnya (Rosen & Greenwood 1976;Dahanukar 2010 tetapi, beberapa penelitian terbaru menunjukkan perbedaan pendapat mengenai masalah tersebut, di mana spesies M. albus komplek dikategorikan sebagai spesies kriptik (cryptic species) (Collins et al 2002;Matsumoto et al 2010;Kottelat 2013). Berbeda dengan hasil sebelumnya (validasi identifikasi BLASTn serta variasi fenotipik berdasarkan atribut eksternal), maka analisis keragaman morfometrik dan genetik gen COI ikan belut sawah menunjukkan hasil yang sama dengan hasil penelitian yang ditemukan oleh Collins et al (2002); Matsumoto et al (2010), bahwa M. albus terdiri atas beberapa spesies kriptik.…”

“…Berbeda dengan hasil sebelumnya (validasi identifikasi BLASTn serta variasi fenotipik berdasarkan atribut eksternal), maka analisis keragaman morfometrik dan genetik gen COI ikan belut sawah menunjukkan hasil yang sama dengan hasil penelitian yang ditemukan oleh Collins et al (2002); Matsumoto et al (2010), bahwa M. albus terdiri atas beberapa spesies kriptik. Hal tersebut jelas terlihat dari hasil pengelompokan ikan belut sawah asal Jawa Barat ke dalam dua klaster utama berdasarkan analisis klaster karakter morfometrik dan pohon filogenetik gen COI.…”

“…Percampuran genetik antara populasi disebabkan oleh beberapa faktor seperti aliran genetik (gene flow) (Laudien et al 2003), maupun aktivitas introduksi oleh manusia Gambar 6 Dendrogram hubungan kekerabatan empat populasi belut sawah berdasarkan keragaman morfometrik menggunakan metode klaster Hirarkis-jarak Euclidean. (Collins et al 2002). Proses gene flow sering kali dikaitkan dengan jarak geografis suatu populasi.…”