Najas Minor (Hydrocharitaceae) in North America: a Reappraisal

Home , Najas gracillima, Najas minor

Aquatic Botany 126 (2015) 60–72

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Aquatic Botany

journal homepage: www.elsevier.com/locate/aquabot

Najas minor (Hydrocharitaceae) in North America: A reappraisal

a,∗ a,1 a,2 a,3

Donald H. Les , Elena L. Peredo , Nicholas P. Tippery , Lori K. Benoit ,

a a b,4 b c

Hamid Razifard , Ursula M. King , Hye Ryun Na , Hong-Keun Choi , Lei Chen ,

a,5 d

Robynn K. Shannon , Sallie P. Sheldon

Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, CT 06269-3043, USA

Department of Biological Sciences, Ajou University, Suwon 443-749, Republic of Korea

South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650, China

Department of Biology, Middlebury College, Middlebury, VT 05753-6151, USA

a r t i c l e i n f o a b s t r a c t

Article history: Genetic studies of nonindigenous populations can help to determine their geographical origin, whether

Received 19 March 2015

single or multiple introductions have occurred, and provide evidence of hybridization. We broadly sur-

Received in revised form 16 June 2015

veyed Najas minor populations at several nuclear and chloroplast loci. Sequence data were obtained from

Accepted 23 June 2015

nonindigenous N. minor populations in North America and portions of its native range in Europe (Italy)

Available online 29 June 2015

and Asia (China, Korea). North American populations were mapped to evaluate the observed patterns of

genetic variation geographically. We detected multiple genotypes of N. minor in collections originating

Key words:

from within Eurasia and North America. In North America, the presence of two, distinct, widespread

Aquatic plant

genotypes indicated at least two separate introductions. These genotypes shared partial genetic similar-

Genetic variation

Hybridization ity with accessions from China. Two other genotypes (restricted to Michigan, Ohio, and West Virginia)

Invasive represented either additional introductions of hybrid plants, and/or post-introduction hybrid events that

Multiple introduction occurred in North America. The existence of several genotypes among nonindigenous North American

Najas oguraensis N. minor populations indicates a history of multiple introductions, and raises concerns over the poten-

Nonindigenous

tial proliferation of novel hybrid genotypes in this region. Because the two main genotypes essentially

Weed

remain allopatric, management efforts should focus on preventing their contact, which could result in

proliferation of hybrid plants with enhanced invasive attributes.

1. Introduction

About 5000 nonindigenous plant species have become natural-

ized in North America, many as noxious weeds (Morse et al., 1995).

Aquatic habitats are particularly susceptible to plant invasions.

Wetlands harbor nearly a fourth of the world’s seriously invasive

∗

Corresponding author. Fax: +1 860 486 6364.

species (Zedler and Kercher, 2004) and numerous water bodies

E-mail addresses: [email protected]

have become infested with nuisance hydrophytes (Pieterse and

(D.H. Les), [email protected] (E.L. Peredo), [email protected] (N.P. Tippery),

Murphy, 1993). Introduced aquatic plants impact native habitats,

lori [email protected] (L.K. Benoit), [email protected] (H. Razifard),

[email protected] (U.M. King), [email protected] (H.R. Na), [email protected] interfere with navigation and recreation, and infest agricultural sys-

(H.-K. Choi), [email protected] (L. Chen), [email protected]

tems that cultivate rice and other water plants (Pimentel et al.,

(R.K. Shannon), [email protected] (S.P. Sheldon).

1 2001). Such introductions are devastating economically, costing the

Present address: The Ecosystems Center, Marine Biological Laboratory, 7 MBL

United States over $100 million each year for control programs, and

Street, Woods Hole, Massachusetts, 02543, USA.

Present address: Department of Biological Sciences, University of Wisconsin- an additional $10 million in related economic losses (Pimentel et al.,

Whitewater, Whitewater, Wisconsin, 53190, USA. 2001; Lovell et al., 2006). Some estimates have ranked these annual

Present address: U.S. Fish and Wildlife Service, 50 Bend Road, Charlestown,

losses at $1-10 billion (Rockwell, 2003).

Rhode Island, 02813, USA.

4 It is necessary to understand nonindigenous species distri-

Present address: Northeastern Asia Plant Institute, Seoul, 135-943, Republic of

Korea. butions to evaluate source(s) of introduction (Les et al., 2013),

Present address: College of Science and Technology, Fairmont State University, potential for spread in natural communities (Les and Mehrhoff,

Fairmont, West Virginia, 26554, USA.

http://dx.doi.org/10.1016/j.aquabot.2015.06.005

D.H. Les et al. / Aquatic Botany 126 (2015) 60–72 61

Table 1

1999), and ecological factors pertaining to their place of origin,

Earliest North American state or provincial* records of Najas minor based on pub-

all which may help to elucidate management strategies (Müller-

lished accounts or herbarium records (LSU; CONN). Genotypes determined by this

Schärer et al., 2004). It also is important to determine whether

study are indicated (n/a = material not evaluated; n/a** = region searched but no

multiple introductions occur because such events can confer high material located).

adaptive potential to invaders by increasing genetic diversity

Locality Year Source This study

through intraspeciﬁc recombination or interspeciﬁc hybridization

OH 1932 Wentz and Stuckey (1971) USA-1; nrITS-1/pdsG

(Genton et al., 2005; Lavergne and Molofsky, 2007; Culley and

NY 1934 Clausen (1936) USA-2

Hardiman, 2009; Schierenbeck and Ellstrand, 2009). Genetic stud-

AL 1943 Meriläinen (1968) USA-1

ies of invasive species also help to characterize their competitive

TN 1944 Meriläinen (1968) n/a

potential (Bossdorf et al., 2005), provide evidence of hybridization WV 1947 Meriläinen (1968) USA-1; nrITS-2/pdsR

MI 1949 Wentz and Stuckey (1971) USA-1; nrITS-1/pdsG

with native species (Moody and Les, 2002), and clarify taxonomic

GA 1951 EDDMapS (2014) USA-1

issues pertaining to submersed plants, whose highly reduced mor-

PA 1951 EDDMapS (2014) USA-1

phologies render them prone to misidentiﬁcation (Les et al., 2006).

FL 1958 Meriläinen (1968) USA-1

Najas ranks among the roughly three percent of plants compris- IN 1958 Wentz and Stuckey (1971) USA-1

ing major aquatic weeds worldwide (Sidorkewicj et al., 2004). IL 1963 Meriläinen (1968) USA-1

VT 1965 EDDMapS (2014) USA-2

Najas minor All. was introduced to North America in the early 20th

SC 1969 EDDMapS (2014) USA-1

century (Meriläinen, 1968; Wentz and Stuckey, 1971). Although

KY 1974 This study (LSU) USA-1

generally not problematic in its native range (where it tends to be

MA 1974 EDDMapS (2014) USA-2

rare), N. minor has become widespread in North America where AR 1979 EDDMapS (2014) USA-1

MS 1979 EDDMapS (2014) USA-1

it displaces native plants and interferes with recreational activi-

OK 1979 Nelson and Couch (1981) USA-1

ties (Fig. S1). It is listed as a noxious weed in several U.S. states

LA 1980 Sullivan (1981) n/a**

(USDA, 2012). Its method of introduction is unknown, but has

MD 1982 EDDMapS (2014) USA-1

been attributed to escapes from cultivation or waterfowl food plant VA 1985 EDDMapS (2014) USA-1

propagation programs (Les and Mehrhoff, 1999). MO 1990 EDDMapS (2014) USA-1

NH 1992 Padgett and Crow (1993) n/a

N. minor is a submersed, water-pollinated, freshwater annual

CT 1995 This study (CONN) USA-2

whose historical native distribution once extended throughout

NC 1964 Radford et al. (1964) n/a**

Eurasia and northern Africa (Triest, 1988). This sexual species dis-

IA 1998 EDDMapS (2014) USA-2

perses primarily by seeds, given that asexual reproduction (by ON* 1999 Smith (2003) n/a

DE <2000 Haynes (2000) n/a**

shoot fragmentation) is inefﬁcient and provides no means of over-

MN 2001 EDDMapS (2014) USA-1

wintering. Despite its former presence, occurrences have dwindled

CA 2003 Les et al. (2012) USA-2

in Western Europe (Casper and Krausch, 1980), with few additional

SD 2006 Larson (2010) n/a

20th century records (Triest, 1988). The species also is endangered KS 2007 Morse et al. (2007) USA-1

in Japan (JIBIS, 2012) and rare in Hong Kong (Yip et al., 2010). Col- WI 2007 Skawinski (2010) USA-2

NJ 2008 EDDMapS (2014) USA-2

lections from rice ﬁelds in Azerbaijan, China, Italy, Iran, Japan, and

TX 2010 Les et al. (2012) USA-1

Turkey (Triest, 1988) indicate alterations to the original distribu-

tion of N. minor by human-mediated dispersal. Consequently, it can

anomalies prompted us to reevaluate the current distribution of N.

be difﬁcult to determine whether records of N. minor, even within

minor in North America in order to clarify the geographical origin

its original native range, represent indigenous or non-indigenous

of the nonindigenous populations.

populations. Contaminated planting stocks also have introduced

Najas species to rice ﬁelds in Australia and California (McIntyre

2. Methods

and Barrett, 1985). California introductions include N. gracillima (A.

Braun ex Engelm.) Magnus, N. graminea Delile, and N. minor (Les

2.1. Sampling

et al., 2012, 2013).

N. minor is distinct taxonomically by its laterally striate seed are-

All authors participated in surveying more than 1500 potential

oles, a generic feature shared only with N. oguraensis Miki (Triest,

Najas habitats in North America or Asia during ﬁeld work con-

1988). These taxa have been distinguished by their unilocular

ducted from 2009 to 2012. About a third of American sites surveyed

(N. minor) or quadrilocular (N. oguraensis) anthers (Triest, 1988),

contained one or more Najas species (Fig. 1a). We also included sev-

although otherwise they are virtually impossible to differentiate

eral N. minor specimens (from MA, MN, WI) sent by colleagues or

morphologically. Vegetative N. minor material requires genetic

sampled with permission from herbarium material (CDA, CONN).

analysis for conﬁdent identiﬁcation. In North America, N. minor

These activities procured 109 N. minor accessions from 28 states

often is misidentiﬁed as N. gracillima or N. marina L. (Wentz and

for DNA analysis (Fig. 1b; Table 1; Appendix). Eleven specimens

Stuckey, 1971; Les et al., 2012, 2013). Slender vegetative forms can

of N. minor and material identiﬁed as N. oguraensis (by anther

resemble N. gracillima and are difﬁcult to identify in the absence of

morphology) were collected in China and Korea; an Italian spec-

seeds (Les et al., 2013). Misidentiﬁcations as N. marina result largely

imen was provided by C. D. K. Cook. Najas gracillima A. Braun ex

from keys written only to accommodate the native North Ameri-

Magnus was collected from 13 sites in the United States (CA, CT,

can species. Prior to the introduction of N. minor, N. marina was the

MN, MO, PA, RI, and TN) and Korea. Altogether, 134 accessions

only North American Najas species having prominently toothed leaf

were evaluated (Appendix). Field-collected plants were preserved

margins, a distinction often made in the initial couplet of identiﬁ-

in CTAB (Rogstad, 1992) and as herbarium vouchers (AJOU, CONN,

cation keys. In such cases, N. minor (also conspicuously toothed)

or SCBG; Appendix). California material was collected under East

would key out incorrectly as N. marina (Les et al., 2012).

Bay Regional Parks permit #596.

The present work was undertaken in conjunction with an ongo-

ing systematic study of North American Najas taxa by the principal

author. During routine collecting for that project, N. minor vouch- 2.2. Mapping

ers were acquired with material preserved for genetic analysis

throughout the region. While processing these accessions, multi- North American ﬁeld sites were georeferenced using a GPSmap

ple genotypes and geographical disjunctions were disclosed. These 76CS unit (Garmin International, Olathe, KS). Other accessions Download English Version: https://daneshyari.com/en/article/6381741

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