SYNTHESIS & INTEGRATION On biodiversity and conservation of the Iris hexagona complex (Phaeiris, Iridaceae) 1, 2 3 1 EVGENY V. M AVRODIEV, JUAN P. G OMEZ, NICHOLAS E. MAVRODIEV, ANTHONY E. MELTON, 4 4 1 1 MARIO MARTINEZ-AZORIN, MANUEL B. CRESPO, SCOTT K. ROBINSON, AND DAVID W. STEADMAN 1Florida Museum of Natural History, University of Florida, PO Box 117800, Gainesville, Florida 32611 USA 2Departamento de Quımica y Biologıa, Universidad del Norte, Km 5 Vıa a Pto. Colombia, Barranquilla, Colombia 3Cornerstone Academy, 1520 NW 34th Street, Gainesville, Florida 32605 USA 4Departamento de Ciencias Ambientales y Recursos Naturales (Botanica), Universidad de Alicante, Apartado 99, Alicante E-03080 Spain Citation: Mavrodiev, E. V., J. P. Gomez, N. E. Mavrodiev, A. E. Melton, M. Martınez-Azorın, M. B. Crespo, S. K. Robinson, and D. W. Steadman. 2020. On biodiversity and conservation of the Iris hexagona complex (Phaeiris, Iridaceae). Ecosphere 12(1):e03331. 10.1002/ecs2.3331 Abstract. Taxonomic revisions using newly available molecular data can have profound consequences for identifying areas of high endemism and, therefore, high conservation priority. A good example of the con- nection between taxonomy, biodiversity ecology, and conservation issues is genus Phaeiris (Iris subsect. Hexagonae), an endemic taxon of the southeastern United States and in particular P. hexagona (I. hexagona) (Blue Flag), perhaps the best-known species of this genus. Some authors recently provided evidence for the need to revise the taxonomy of the Blue Flag, which has usually been considered to consist of a single species, P. hexagona. Using molecular and bioclimatic analyses of Blue Flags from Florida and Louisiana, collected at their loci classici, we challenge the notion that P. hexagona is a single species, referring to the almost forgotten taxonomic context of Phaeiris as established by John K. Small and Edward J. Alexander nearly 90 yr ago. Our vision of the P. hexagona complex reinforces the current treatment of Southern Coastal Plain as a biodiversity hotspot. Our results also argue for the complex nature of endemism on the Florida Peninsula, and elsewhere on the Southern Coastal Plain, including a new interpretation of the well-studied Louisiana irises. We also propose that the valleys of Florida rivers and lakes are likely to harbor additional hidden biodiversity. Accu- rate taxonomy proved to be a heuristic tool to characterize better the actual level of biodiversity within Southern Coastal Plain as well as to describe the different areas endemism. The newly re-documented taxo- nomic diversity in broadly defined P. hexagona should also be considered in future conservation efforts. Key words: bioclimatic analysis; Florida Peninsula; Louisiana irises; molecular phylogeny. Received 6 May 2020; accepted 13 May 2020; final version received 11 November 2020. Corresponding Editor: Debra P. C. Peters. Copyright: © 2021 The Authors. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. E-mail: evgeny@ufl.edu The watersheds of different rivers commonly harbor flags identify many cryptic, unrecognized, or simply of a single species or endemic plants. Small (1927:11). forgotten taxonomic entities (e.g., Mavrodiev et al. 2012a,b,c, 2013, 2014, 2015a, Yurtseva et al. INTRODUCTION 2016a,b, among others), some of which are poten- tially in need of conservation attention. Such new Modern phylogenetic methods, especially analyses have also provided new information on molecular approaches, have made it possible to the prevalence of previously unrecognized areas v www.esajournals.org 1 January 2021 v Volume 12(1) v Article e03331 SYNTHESIS & INTEGRATION MAVRODIEV ET AL. of endemism (Mavrodiev et al. 2012a,b) as well Therefore, we have to discuss: as on the importance of environmental variables 1. the possible cryptic diversity of the Florida that may be fully congruent with the observed Blue Flag, which is impossible without the biodiversity (Mavrodiev et al. 2015b). In this con- general taxonomic outlook on the Louisiana text, the challenging of traditional taxonomic cir- irises; cumscriptions suspected to contain hidden taxa 2. the possible structure of the SCP biodiver- can also be an important tool for both ecologists sity, in particular the possibility of river val- and conservation biologists, especially when leys to be potential sources of cryptic linked with actual or potential biodiversity hot biodiversity; spots (e.g., Mavrodiev et al. 2012a,b, Sokoloff 3. the future of the conservation status of the et al. 2019, see also Liu et al. 2019). Phaeiris hexagona complex, as well as the rest A good example of such a connection of the genus Phaeiris. between taxonomy, ecology, and conservation issues is the genus Phaeiris (I. subsect. Hexagonae; To achieve these goals, we perform bioclimatic Appendix S1), an endemic taxon of the south- and cladistic analyses of all extant non-hybrid eastern United States with its center of diversity taxa of the genus Phaeiris, with special attention in the Coastal Plain, particularly in the Missis- on those related to P. hexagona. sippi River Delta region (e.g., Small and Alexan- At least five related taxa have been segregated der 1931, Crespo et al. 2015). Phaeiris has a high from Phaeiris hexagona (Iris hexagona) in the past potential to contain cryptic or unrecognized spe- (e.g., Small 1930a, Small and Alexander 1931, cies (e.g., Small and Alexander 1931) in need of Foster 1937), namely Phaeiris albispiritus (I. conservation attention (Small 1931) and thus albispiritus; Small 1929a), P. giganticaerulea (I. gi- may also provide insights in identifying areas of ganticaerulea; Small 1929b), P. rivularis nom. prov. endemism and environmental conditions that (I. rivularis; Small 1927), P. kimballiae nom. prov. are congruent to the actual biodiversity of the (I. kimballiae; Small 1925c), and P. savannarum (I. genus. savannarum; Small 1925b; see Table 1 and Phaeiris hexagona (Iris hexagona) (Blue Flag; Appendix S1–S3 for details and complete Small 1925a) is perhaps the best-known species names). of the genus. The major goal of this study is to Today, however, a common belief is that this evaluate critically circumscription of Phaeiris group consists of only one (e.g., Hamlin et al. hexagona in the context of the growing recogni- 2017) to three species (e.g., Meerow et al. 2011; tion that: Table 1). Here we challenge that idea using 1. the Southern Coastal Plain of North Amer- molecular sequence data in a bioclimatic context ica (SCP) is a biodiversity hot spot (Noss thus referring to the almost forgotten taxonomic et al. 2015), and assessment of Phaeiris done long ago by John K. 2. the Florida peninsula, in particular, is an Small and Edward J. Alexander (Small and area of high endemism (reviewed in James Alexander 1931), who described numerous spe- 1961 and Reece and Noss 2014). cies of Phaeiris, mostly from the Mississippi River Table 1. Summary of the taxonomic treatments of Phaeiris hexagona and non-extinct related species referred to in this study. Small and Alexander Viosca (1935); Foster (1937); Hamlin Henderson (2002); Meerow et al. (2007, (1931) et al. (2017) 2011, 2017) This study Iris giganticaerulea Iris hexagona Iris. giganticaerulea Phaeiris giganticaerulea I. hexagona I. hexagona I. hexagona P. hexagona I. kimballiae I. hexagona I. savannarum P. kimballiae I. rivularis ignored I. savannarum P. rivularis I. savannarum I. hexagona I. savannarum P. savannarum v www.esajournals.org 2 January 2021 v Volume 12(1) v Article e03331 SYNTHESIS & INTEGRATION MAVRODIEV ET AL. Delta (Small and Alexander 1931, also see Hen- and Austin et al. 1987). In this context, the high derson 1994). Perhaps because of this, the popular diversity of iridaceous plants (Small 1925a, name of the genus Phaeiris became the Louisiana c,1927,1929a,b,1930a, Small and Alexander 1931) irises (e.g., Viosca 1935, among others). would be just another case of a widespread phe- Surprisingly, the results of Small and Alexan- nomenon. der (1931) soon were criticized by the field natu- The taxonomic interpretation of the blue flags ralist and amateur iridologist Viosca (1935), of Louisiana and Florida indeed has been partly whose primary scientific interests concerned her- challenged by Randolf (1966) and especially by petology, ichthyology, and invertebrate zoology Henderson (2002), Ward (2008, 2011), and (Penn 1962, Boudreaux 1967). Viosca (1935) had Meerow et al. (2007, 2011, 2017). For example, a major influence on the taxonomy of the Louisi- the studies of Hamlin and Arnold (2014, 2015) ana irises (e.g., Anderson 1949, 1961, Riley 1938, that combined the populations of three taxa (Iris Foster 1937, also see Hamlin et al. 2017). In short, giganticaerulea, I. hexagona, and I. savannarum) Viosca argued that only three species from Iris under I. hexagona “... may be more a scenario of subsect. Hexagonae occur in southeastern Louisi- species divergence than population level adapta- ana: Iris foliosa (today conceptualized as a syn- tion” (Meerow et al. 2017:318, see also Meerow onym of I. brevicaulis; Henderson 2002), I. fulva, et al. 2011). and I. giganticaerulea (Viosca 1935), the actual In this study, we continue the molecular inves- synonym of I. hexagona (Viosca 1935; Table 1). tigation of the non-hybrid species of Phaeiris in The natural hybrids between I. fulva and I. hexag- Florida and Louisiana. We evaluate