Cryptic species of pondweeds (Potamogetonaceae) at an intercontinental scale revealed by molecular phylogenetic analyses

Abstract

Cryptic species are morphologically indistinguishable but genetically divergent entities that constitute an important part of Earth's biodiversity. They occur in all kingdoms of life, especially when morphological characters are scarce. Compared to the high number of plant species, relatively few cryptic species have been detected so far. Here, we report cryptic species in pondweeds (Potamogeton), freshwater aquatic angiosperms that are characterized by reduced morphology. Using four molecular markers (ITS, 5S‐NTS, rpl20‐5′rps12, trnT‐trnL), three of them unlinked, we found that the widespread P. octandrus consists of three divergent lineages that correspond to the geographic origins of samples from Africa, Asia, and Australia, respectively. Relatively high genetic divergence between these lineages, reciprocal monophyly and many fixed diagnostic characters indicate that P. octandrus consists of three cryptic species. We formally distinguish the African lineage as P. parvifolius and the Australian lineage as P. tenuicaulis from Asian P. octandrus s.str. Potamogeton tenuicaulis is paraphyletic with the Asian species P. cristatus, which differs by unique fruit characters. We assume that the ancestor of P. cristatus originated from Australia and reached Asia by long‐distance dispersal. Quality criteria for assigning species status to cryptic species and their formal taxonomic recognition are discussed.

Evolutionary history and patterns of geographical variation, fertility, and hybridization in Stuckenia (Potamogetonaceae)

“…In the case of S. pectinata , there are obvious differences in the fertility of particular genotypes, and some of them correspond to particular morphological forms and/or geographic areas. We assume that we are observing here some incipient speciation and that some genotypes may already represent cryptic species, as it was also found in the sister genus Potamogeton ( Aykurt et al., 2020 ; Fehrer et al., 2022 ). However, without a deeper understanding of intraspecific processes—and given that all genotypes of S. pectinata together form monophyletic clades with all markers, which are genetically widely divergent from other species (except S. striata , with which it is paraphyletic)—it would be unwise to propose taxonomic consequences at the intraspecific level.…”

“…This is also evident for 5S-NTS sequences. Even though they are much more polymorphic and less well homogenized than ITS sequences in Stuckenia (but less than in the sister genus Potamogeton , Kaplan et al., 2018 ; Fehrer et al., 2022 ), the dominant sequence types clearly reveal many distinct genotypes within each of the three widespread species that fit well with the geographical origins of the samples. ITS sequences also reveal geographical structure at the intraspecific level but it is less prominent due to the low variation of the marker.…”

“…In the sister genus Potamogeton , like in most angiosperms, plastid DNA is inherited maternally ( Kaplan and Fehrer, 2006 ), and we, therefore, assume that this is also the case with Stuckenia . All these markers have proved suitable to resolve species relationships in Potamogeton (e.g., Iida et al., 2004 ; Lindqvist et al., 2006 ; Kaplan and Fehrer, 2011 ; Kaplan et al., 2013 ; Ito et al., 2016 ; Kaplan et al., 2018 ; Fehrer et al., 2022 ), and some of them have also been applied in Stuckenia ( Iida et al., 2004 ; Lindqvist et al., 2006 ; Wang et al., 2007 ; Zhang et al., 2008 ; Du and Wang, 2016 ; Kuzmina et al., 2017 ; Volkova et al., 2017 ).…”

A Multigene Phylogeny of Native American Hawkweeds (Hieracium Subgen. Chionoracium, Cichorieae, Asteraceae): Origin, Speciation Patterns, and Migration Routes

“…The disjunct distribution of H. antarcticum and H. gracile / H. triste can be best explained by long distance dispersal mediated by migratory birds, which has been described or inferred for various terrestrial and aquatic plants [ 79 , 80 , 81 , 82 ]. There exist three flyways of migratory birds of the order Charadriiformes that range from the high latitudes of North America to Patagonia [ 83 ].…”

Speciation and conservation genetic assessment of two endangered cycad species

“…Furthermore, it is mysterious that some species pairs are morphologically similar but can be recognized using molecular markers (i.e., cryptic species) (Bickford et al, 2007), such as species in Taxus (Taxaceae) (Liu et al, 2011), Pinus armandii Franch. (Pinaceae) (Liu et al, 2019), Zamia integrifolia L.f. (Zamiaceae) (Griffith et al, 2022), and Potamogeton (Potamogetonaceae) (Fehrer et al, 2022). Comparing patterns of intra‐ and interspecific genetic differentiation between species with similar morphology holds considerable significance in unraveling the mechanisms underlying their speciation process.…”