Mitochondrial DNA Sequence, Morphology and Ecology Yield Contrasting Conservation Implications for Two Threatened Buckmoths (Hemileuca: Saturniidae)
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BIOLOGICAL CONSERVATION Biological Conservation 118 (2004) 341–351 www.elsevier.com/locate/biocon Mitochondrial DNA sequence, morphology and ecology yield contrasting conservation implications for two threatened buckmoths (Hemileuca: Saturniidae) Daniel Rubinoff a,*, Felix A.H. Sperling b a Department of Plant and Environmental Protection Sciences, University of HawaiÕi, 310 Gilmore Hall, 3050 Maile Way, Honolulu, HI, 96822 USA b Department of Biological Sciences, University of Alberta, CW405A Biological Sciences Ctr., Edmonton, Alta., Canada T6G 2E9 Received 9 April 2003; received in revised form 17 September 2003; accepted 22 September 2003 Abstract Taxa of conservation interest are frequently identified using morphological or ecological characters. These characters are as- sumed to represent evolutionary importance, population structure and/or phylogenetic relationships in such organisms. We tested this assumption using two species complexes of the moth genus Hemileuca (Saturniidae). Both have populations threatened by habitat loss and need conservation protection. Legislation protects one taxon with apparent ecological differences. We sequenced 624 base pairs of mtDNA from the COI gene for geographically distant populations of the Hemileuca maia species complex and the H. electra species complex. Resultant phylogenies contradict prior assumptions about relationships in both species complexes. The legislatively protected Bog Buckmoth is paraphyletic with widespread H. maia, and its use of a novel hostplant seems to be a local adaptation. Divergent morphology and hostplant use among H. electra subspecies are associated with modest genetic divergence (0.48%). However, a group of unrecognized populations that are morphologically similar and geographically close to H. electra electra have mtDNA that is divergent by an average of 4.1%. There is disagreement regarding prioritization of ecological divergence over neutral genetic distance in conservation. We place ecological variation in a phylogenetic context and recommend that ex- ploration of genetic relationships be undertaken when populations are threatened. Adaptive ecological variation should be evaluated in a phylogenetic context to understand its conservation importance. This study illustrates the importance both of phylogenetic context and the use of independent characters in assessing biodiversity for conservation prioritization. Ó 2003 Elsevier Ltd. All rights reserved. Keywords: Systematics; Insect conservation; Conservation prioritization; Cryptic species; Genetic distance; Adaptive ecological variation 1. Introduction between very similar populations (Daugherty et al., 1990; Baker et al., 1995; Burbrink et al., 2000; Dawood Identification of unique populations or species that and Channing, 2000; Lee, 2000). As a result, conserva- are considered to represent independent, historically tion attention will be focused on what are actually isolated, evolutionary lineages is often based solely on widespread, relatively undifferentiated populations, morphological or ecological traits (Moritz, 1994). These while much older lineages are left unrecognized and traits become the basis for assigning conservation value unprotected (May, 1990). Systematists generally agree to unique populations. However, phylogenetic rela- that conservation efforts should be focused on phylo- tionships established by morphological or ecological genetically distinct taxa, since such ‘‘long branches’’ characters may fail to recognize cryptic species, or ex- represent more evolutionary time than the ‘‘bush phy- aggerate what are actually modest genetic differences logenies’’ of recently diverged lineages (May, 1990; Vane-Wright et al., 1991; Faith, 1994; Crozier, 1997; * Corresponding author. Moritz, 2002 but see Erwin, 1991; Crandall et al., 2000). E-mail addresses: rubinoff@hawaii.edu (D. Rubinoff), A lack of systematic knowledge for potentially [email protected] (F.A.H. Sperling). threatened taxa thus precludes effective conservation 0006-3207/$ - see front matter Ó 2003 Elsevier Ltd. All rights reserved. doi:10.1016/j.biocon.2003.09.013 342 D. Rubinoff, F.A.H. Sperling / Biological Conservation 118 (2004) 341–351 prioritization (Daugherty et al., 1990). In such situa- not restricted to Menyanthes and are commonly found tions, molecular systematics can play a crucial role in the on other genera like Salix and Betula, especially in the identification and conservation of threatened taxa later larval instars. Furthermore, polyphagy is well es- (Haig, 1998; Soltis and Gitzendanner, 1999). tablished in some populations of H. maia and H. ne- The North American moth genus Hemileuca Walker vadensis (Scholtens and Wagner, 1994; Martinat et al., (Saturniidae) contains approximately 20 species, in- 1997; Pryor, 1998). Legge et al. (1996) and Tuskes et al. cluding two taxa that are threatened: the Bog Buck- (1996) assert that the Bog Buckmoth is an independent moth, which is a member of the maia species complex evolutionary lineage, having arisen out of populations that has no formal scientific name (Tuskes et al., 1996) of the western species H. nevadensis that became isolated and Hemileuca electra electra Wright, one of four sub- during interglacial periods. However, there are few species of the H. electra complex. Both species com- ecological or morphological differences between the Bog plexes have been the subjects of intensive morphological Buckmoth and parapatric populations of H. maia to the and ecological investigations to determine systematic east and south and H. nevadensis to the west (Fig. 1), relationships (Scholtens and Wagner, 1994, 1997; Tus- leading to suggestions that the maia complex may ac- kes and McElfresh, 1995; Legge et al., 1996; Tuskes tually represent one variable species using many habitats et al., 1996). Even so only limited, and inconclusive, and hostplants (Scholtens and Wagner, 1997; Kruse, genetic data have been gathered on the Bog Buckmoth 1998). (Legge et al., 1996) and nothing is known of the genetic The H. electra species complex contains four mor- relationships among the four electra subspecies. The phologically distinct subspecies that range across parts electra and maia species complexes represent a rich of southwestern California (electra), southeastern Cali- model for examining how well systematic relationships fornia and southern Nevada (mojavensis Tuskes and based on morphological and ecological characters pre- McElfresh), northern Arizona (clio Barnes and dict genetic relationships between taxa, especially those McDunnough), and Baja Norte, Mexico (rubra McEl- pertinent to conservation prioritization. fresh and Tuskes) (Table 1 and Fig. 2). The nominate The Bog Buckmoth (Hemileuca sp., Tuskes et al., subspecies, H. electra electra, is found predominantly in 1996) is a legislatively protected taxon restricted to a few coastal sage scrub, a habitat which has been greatly re- bogs in the Great Lakes region of North America, al- duced by urban development (Westman, 1981). Never- though debate has arisen over the evolutionary origins theless, no conservation status has been suggested for and phylogenetic distinctness of the Bog Buckmoth H. electra electra, even though Tuskes and McElfresh (Legge et al., 1996; Scholtens and Wagner, 1997; Kruse, (1995) raised concern about the future of the taxon, and 1998). It is differentiated from its putative sister species, Rubinoff (2001) found that it was not adequately pro- H. maia (Drury) and H. nevadensis Stretch, solely by its tected by current reserve designs. This inaction is based occurrence in bog habitats and its ability to feed on bog on morphological and ecological characters that suggest buckbean, Menyanthes trifoliata (Menyanthaceae) as a that the H. electra electra phenotype is a coastal form larva (Tuskes et al., 1996). Yet Bog Buckmoth larvae are that blends eastward into adjacent Colorado Desert Fig. 1. Range map for the Hemileuca maia complex (Tuskes et al., 1996). Collection localities are denoted by black circles. D. Rubinoff, F.A.H. Sperling / Biological Conservation 118 (2004) 341–351 343 Table 1 Populations of Hemileuca sampled (names from Tuskes et al., 1996) Taxon Collection locality Number of individuals sequenced Maia complex H. maia NY: Suffolk Co. 2 H. maia FL: Clay Co. 1 H. maia LA: Livingston Parrish 2 BBMa;b NY: Oswego Co. 4 BBMa WI: Marquette Co. 2 BBMa WI: Ozaukee Co. 1 H. nevadensis CA: Merced Co. 1 H. nevadensis NV: Lyon Co. 2 H. nevadensis WI: Douglas Co. 1 Electra complex H. electra electra CA: San Diego Co. 6 H. electra electra CA: Riverside Co. 1 H. electra clio AZ: Gila Co. 2 H. electra rubra MX: Baja Calif., Catavina 2 H. electra mojavensis CA: San Bernardino Co. 2 Colorado Desert popsa CA: Imperial Co. 5 Colorado Desert popsa CA: Riverside Co. 2 Colorado Desert popsa CA: San Diego Co. 1 Outgroup taxa H. eglanterina CA: Mono Co. 1 H. griffini AZ: Coconino Co. 1 H. burnsi CA: San Bernardino Co. 1 H. neumogeni UT: Washington Co. 1 H. juno AZ: Cochise Co. 1 H. oliviae NM: Lincoln Co. 1 a Undescribed taxa, BBM is the Bog Buckmoth. b Taxon with legislative protection. Fig. 2. Range map for the Hemileuca electra complex (Tuskes and McElfresh, 1995). Collection localities are denoted by black circles. 344 D. Rubinoff, F.A.H. Sperling / Biological Conservation 118 (2004) 341–351 populations that are not currently threatened (Tuskes We obtained samples of all four H. electra subspecies and McElfresh, 1995). These Colorado Desert popula- and the unnamed Colorado Desert populations (Table 1 tions are insufficiently