Phylogeography and conservation
Unraveling natural diversity
The genus Najas comprises approximately 50 species of cosmopolitan, unisexual
(diclinous), submersed, aquatic plants. The genus Najas is composed of over 50 species, all of them obligate aquatics. One of the more striking characteristics of the water nymphs is that they are one of the few plants able to develop their complete vital cycle, including pollination, underwater. Like many aquatic angiosperms, the species are extremely reduced morphologically and exhibit extensive phenotypic plasticity in vegetative traits. These factors confound attempts to evaluate systematic relationships or develop an effective taxonomic treatment for the group. Some of the possible sources of morphological variation are elevated ploidy levels, the existence of cryptic species, and even the presence of inconspicuous hybrids both recent and established. In our research, we sampled material from more than a thousand sites, sequence fresh, and voucher accession all across the globe. We have discovered new sites for native and non-native Najas species, hybrids, events of cryptic speciation, and new introductions of non-native species...
Research at Les Lab University of Connecticut
NSF DEB Collaborative Research: Systematic and ecological studies of North American Najas L. (Hydrocharitaceae)
Who are you? And .... what are you doing here!
Reduced morphology and huge intraspecific variation lead to taxonomic problems that are even more accused at the species level. One paradigmatic case of this taxonomical confusion is N.guadalupensis, the most widely distributed taxon in the New World. Often has been confused with other Najas species (e.g., N. flexilis, N. wrightiana). This species exhibits a wide array of characteristics that has complicated the attempts to define cohesive infraspecific taxa although it has been subdivided into several taxa using morphological characters. Our results indicate that the morphological variation is not only related to the existence of specific locally adapted subtaxa along the distribution of the species but also frequent hybridization events. Similar situations could be described in other species of the genus, such as N. marina, N. flexilis, N. graminea.
Reduced morphology and lack of distinctive features for taxonomical identification have also made extremely difficult the detection of non-native species. Old World species such as N. graminea or N. minor are nowadays present in USA. Their introduction has been frequently related to unintentional co-culture in rice fields and water-gardening areas. Najas species have shown great ability to survive and thrive in new habitats, even becoming invasive. The high invasive and hybridization potential, together with the cosmopolitan distribution of some Najas species allows silent invasion of non-native genotypes.
Read more:
Les DH, EL Peredo, N Tippery, L Benoit, H Razifard, U King, H Na, H Choi, L Chen, R Shannon, S Sheldon,(2015) Najas minor (Hydrocharitaceae) in North America: a reappraisal. Aquatic Bot 126:60–72.
Les DH, EL Peredo, U King, L Benoit, NP Tippery, C Ball, R Shannon (2015) Through thick and thin: cryptic sympatric speciation in the submersed genus Najas (Hydrocharitaceae). Mol Phylog and Evol 82: 15–30.
D Les, EL Peredo, L Benoit, N Tippery, U King, S Sheldon. (2013) Phytogeography of Najas gracillima (Hydrocharitaceae) in North America and its cryptic introduction to California. Am J of Bot 100:1905-15
D Les, EL Peredo, U King, N Tippery. In guad we trust? Exposing the real Najas guadalupensis (Hydrocharitaceae). Botany 2014. The Boise Centre (ID) 26-30 July2014.
Cryptic Speciation
Cryptic sympatric speciation combines several concepts, wherein species exhibit incomplete morphological distinctness and persist within overlapping geographical ranges. Cryptic species are closely related but genetically divergent lineages that are difficult or impossible to distinguish phenotypically, leading to their frequent categorization under a single taxonomic name. Cryptic species have been reported commonly among aquatic (e.g., marine) animals and protists. Likewise, submersed freshwater angiosperms are ideal candidates for studying cryptic speciation. Aquatic flowering plants exhibit broad, even cosmopolitan geographical distributions, increasing the probability of speciation events in sympatry. However, their extreme morphological reduction and phenotypic plasticity can complicate the detection and suitability of taxonomic markers, thereby hampering the discovery of cryptic lineages. It also is possible that convergent adaptations to the uniform aquatic environment could go unnoticed, thus also masking diverging lineages. Conceivably, the relatively high incidence of polyploidy in aquatic angiosperms provides ample opportunity for rapid reproductive isolation.
Our research uncovered that Najas flexilis s.l. comprises two genetically distinct, sibling species, N. flexilis (exclusively present in North America) and N. canadensis (present also in Europe). Both N. flexilis and N. canadensis occur sympatrically throughout a broad portion of North America, a long-maintained distribution as evidenced by the fossil record. Our research has simplified the taxonomy of the cosmopolitan Najas marina, currently viewed as comprising 12 subspecies with six varieties. This is the only dioecious species in an otherwise monoecious group of annual hydrophiles and resolves phylogenetically as the sister to the remainder of the genus. In contrast to the currently proposed taxonomy, an analysis of DNA sequence data for 22 globally distributed populations resolves only two distinct lineages within N. marina.
Ursula King is continuing the research on Najas, with special emphasis on chloroplast genome evolution across the genus. ursula.king at uconn.edu | Department of Ecology and Evolutionary Biology, University of Connecticut, 75 N. Eagleville Rd., Storrs, CT 06269-3043, USA
DH Les, EL Peredo, UM King, LK Benoit, NP Tippery, C Ball, R Shannon. (2015) Through thick and thin: cryptic sympatric speciation in the submersed genus Najas (Hydrocharitaceae). Molecular Phylogenetics and Evolution 82: 15-30.
EL Peredo, D Les, L Benoit, N Tippery. Cryptic speciation in Najas marina. Botany 2011, Saint Louis (MO) 9-13 July 2011
In collaboration with the Jardín Botánico Atlántico de Gijón I applied molecular markers to understand the history of the Iberian endemic species Senecio boissieri. Senecio boissieri presents disjunct distribution in the Iberian Peninsula. It can be found in the alpine ecosystems of the southern Sierra Nevada and Baza, centrally located Sierra Guadarrama, and northern Cordillera Cantábrica. RAPD analysis identified two divergent genetic groups, one containing individuals from the Cordillera Cantábrica and another comprising individuals from the three other mountain ranges. It is feasible that RAPD divergence in the Cantabrian material reflects the divergence of populations that survived the last glacial maximum in a northern refugium, isolated from the main distribution of the species spanning the area between the southern and central Spanish sierras. Postglacial fragmentation of the species range in southern and central Iberia would have resulted in the current disjunction of genetically similar populations in southern and centrally located mountains.
Partially funded by the Spanish Ministry of Education.
EL Peredo, A Revilla, B Jiménez-Alfaro, A Bueno, JA Fernández Prieto, R Abbott (2009) Historical biogeography of a disjunctly distributed, Spanish alpine plant, Senecio boissieri (Asteraceae). Taxon, 58: 883-892.
Hop cultivars are very similar morphologically and one of the most used techniques to identify each cultivar was the profile of oils in the flower. Using nuclear and chloroplast markers were identified the relationships between wild hops and the currently cultivated ones. Hops has been cultivated for over 5000 years however, due to its asexual reproduction by rhizomes, hops still presents a high genetic diversity. For centuries, the selection of elite cultivars was performed on locally grown hops leading to highly distinctive families of hops varieties across Europe. In the past centuries, germplasm of non-European origin was been introduced into commercial breeding programs. Right now, over 1000 different cultivars are commercially valuable and are being explored to increase features such as the production of oils or resistance to pests and diseases. Microsatellites resulted in a very valuable tool to compare wild to cultivated groups and identify the ancestries of each cultivar. Our main goal was to establish an identification protocol that allowed precise identification of young, adult, and harvested flowers.
Partially funded by the Spanish Ministry of Education.
Desarrollo de metodos biotecnologicos para mejorar la calidad y productividad del lupulo (Humulus lupulus l.) MCYT AGL2002-02472
JL Horreo, EL Peredo, JL Olmedo, J Valladares, E García-Vázquez, MA Revilla. (2014) Genetic Diversity Inferred from Microsatellites of Wild Hops in Galicia (Spain). Brewing Science 67:132-136.
EL Peredo, A Revilla, B Reed, B Javornik, R Arroyo-García (2010) The influence of the European and American wild germplasm in hop cultivars. Gen Res CropEvol, 57: 575-586
