Mangrove estuaries in northwestern Mexico, including the states of Baja California Sur, Sonora, Sinaloa, Nayarit and Jalisco (Aburto-Oropeza et al. 2008), are inhabited by a species in the genus Junonia (Nymphalidae: Nymphalinae) listed as J. evarete (Cramer) by Brown et al. (1992) and referred to as an intermediate between J. evarete zonalis C. Felder & R. Felder and J. coenia Hübner by Hafernik (1982). Recent morphological (Neild 2008; Calhoun 2010) and molecular (Kodandaramaiah & Wahlberg 2007; E. Pfeiler et al., unpublished) studies support the assignment of the mangrove-associated buckeye to the taxon J. genoveva (Cramer), an assignment which is followed here. Ongoing research on Junonia in the Caribbean region, however, suggests that the taxonomy of the mangrove-associated buckeye is more complex than previously thought, probably consisting of more than one species, and that the name used here may ultimately require revision (C. Brévignon, personal communication).
Plant species typically found in mangrove forests in northwestern Mexico include Black mangrove, Avicennia germinans (L.) L. (Acanthaceae), Red mangrove, Rhizophora mangle L. (Rhizophoraceae), White mangrove, Laguncularia racemosa (L.) Gaertn. f. (Combretaceae) and Sweet mangrove, Tricerma phyllanthoides (Benth.) Lundell (Celastraceae). Although J. genoveva has long been known to be associated with the coastal mangrove ecosystem in northwestern Mexico (Hafernik 1982), the larval host plant(s) has remained uncertain. Tilden (1971) suggested the genus Phyla (= Lippia) (Verbenaceae) as a larval host, a genus also used by larvae of the closely related J. coenia in California, USA (Shapiro & Biggs 2010). The genus Stemodia (Scrophulariaceae) was listed as probable larval host (in addition to Phyla) by Brown et al. (1992). Both Hafernik (1982) and Brown et al. (1992) commented on the close association of J. genoveva with the mangrove habitat, but mangroves were not mentioned in either reference as a potential larval host. In the Caribbean region, however, the use of A. germinans as a larval host plant has been well documented (Turner & Parnell 1985; Elster et al. 1999; Brévignon 2009).
Given the ecological association of J. genoveva with mangrove habitat in northwestern Mexico, it was of interest to determine whether A. germinans could be used by larvae of J. genoveva in this region as well. After much searching, five first and second instar larvae of what appeared to be Junonia were found feeding on A. germinans at Estero del Soldado (27°57′35″N, 110°59′00″ W), a small hypersaline lagoon (negative estuary) located on the Gulf of California between Guaymas and San Carlos, Sonora Mexico (Fig. 1). Larvae were collected between 11–22 October 2010 and were provided with fresh leaves of A. germinans every 2–4 days until pupation. Wild-caught adults were taken mainly between 21 July–5 November 2010 at Estero del Soldado and at San Carlos. A population of J. genoveva also was found at a very small mangrove estuary (El Esterito) in San Carlos, 8 km W of Estero del Soldado.
The five larvae fed on A. germinans leaves for approximately 21 days and successfully developed to the last instar and pupated (Fig. 2). One of the five pupae died; the remaining four produced adults (2 males and 2 females) 7–10 days after pupation. One adult female and one adult male were taken as vouchers (Fig. 3); the other two individuals were released. Maculation and coloration of both reared (Figs. 2–3) and wild-caught adults from Estero del Soldado were similar to individuals of J. genoveva figured from coastal regions of Baja California Sur (Brown et al. 1992) and San Blas, Nayarit (Warren et al. 2010; as J. evarete NW Mexican segregate).
The youngest larvae of J. genoveva fed by scraping the upper epidermis of leaves, whereas later instars were chewers. Larvae preferred the younger, fresher tree leaves, although they were originally collected in the wild from older leaves ∼1 m above the water. This feeding behavior differs from that reported in Colombia where larvae of Junonia (listed as J. evarete) were never found more than a few centimeters from the water feeding on propagules, young seedlings and pneumatophores of A. germinans, but not on the mature tree leaves (Elster et al. 1999). Larvae collected in Jamaica also prefer feeding on the cotyledons of young seedlings of A. germinans (Turner & Parnell 1985). The close association between the distribution of A. germinans and J. genoveva in northwestern Mexico (Fig. 1) suggests that A. germinans is the principal host throughout the region. But because of the low numbers of larvae found it was not possible to test for possible alternative hosts. There is evidence, however, suggesting that larvae of Avicennia-feeding Junonia in the Caribbean region are host specific (Turner & Parnell 1985; Elster et al. 1999).
Peak flight activity of J. genoveva at Estero del Soldado occurred from late August through November in agreement with the findings of Brown et al. (1992) in Baja California Sur. Adults showed a preference for bare ground adjacent to the mangroves (Fig. 1). Adults of a large and dark buckeye, recognized as the subspecies J. evarete nigrosuffusa W. Barnes & MeDunnough by Pelham (2008), were also found in the Guaymas/San Carlos region, but this subspecies was never observed flying together with J. genoveva in the immediate vicinity of the mangroves at Estero del Soldado. Both taxa, however, were observed flying on the beach ∼1 km W of Estero del Soldado, and feeding together on Desert broom Baccharis sarothroides A. Gray (Asteraceae) at San Carlos and on ornamental Lantana (Verbenaceae) at a residential complex adjacent to Estero del Soldado. Most observations of J. e. nigrosuffusa, however, were inland from the immediate coast. Thus, the two taxa, although occurring sympatrically, appear to be largely ecologically isolated, similar to the findings in Baja California Sur (Brown et al. 1992).
I wish to thank Wain Evans for photographing the immature stages (Fig. 2) and adults (Fig. 3). I also express my gratitude to R. A. Bailowitz, C. Brévignon, J. P. Brock, J. Calhoun, K. Hansen, J. A. Scott and R. Wells for their helpful comments and insights, and T. Hernández Mendoza for help in the field.