New host-plant records for the defoliator Ormiscodes amphimone (Fabricius) (Lepidoptera: Saturniidae)

Abstract

Ormiscodes amphimone (Fabricius) is a phytophagous moth species known to severely defoliate woody species in Chile and Argentina. Here we document new records of O. amphimonehost associations emphasizing the role of Nothofagus pumilio as its primary host in our study area. This new record for Argentina is highly significant given the economic importance of N. pumilio as a timber resource and the potential of O. amphimone to generate extensive outbreaks.

Defoliation; Hemileucinae; herbivory; insect outbreak; Nothofagus pumilio; Patagonia


SCIENTIFIC NOTE

New host-plant records for the defoliator Ormiscodes amphimone (Fabricius) (Lepidoptera: Saturniidae)

Juan ParitsisI; Mario ElguetaII; Carolina QuinteroIII; Thomas T VeblenI

IDept of Geography, Univ of Colorado, Campus Box 260, 80309-0260 Boulder, CO, USA; paritsis@colorado.edu

IISección Entomología, Museo Nacional de Historia Natural. Casilla 787, Santiago (21), Chile; melgueta@mnhn.cl

IIIDept of Ecology and Evolutionary Biology, Univ of Colorado, Campus Box 334, 80309-0260 Boulder, CO, USA; Carolina.Quintero@colorado.edu

ABSTRACT

Ormiscodes amphimone (Fabricius) is a phytophagous moth species known to severely defoliate woody species in Chile and Argentina. Here we document new records of O. amphimonehost associations emphasizing the role of Nothofagus pumilio as its primary host in our study area. This new record for Argentina is highly significant given the economic importance of N. pumilio as a timber resource and the potential of O. amphimone to generate extensive outbreaks.

Key words: Defoliation, Hemileucinae, herbivory, insect outbreak, Nothofagus pumilio, Patagonia

Ormiscodes species in Chile and Argentina are large phytophagous moths (up to 95 mm wingspan) that feed on a wide variety of plant hosts (Angulo et al 2004). Due to their gregarious behavior during the larval stage and their potential to reach outbreak levels frequently, Ormiscodes amphimone (Fabricius), O. nigrosignata Philippi, and O. cinammomea Feisthamel, are considered detrimental for tree growth and timber production (Bauerle et al 1997).

Ormiscodes amphimone (syn. Ormiscodes marginata Philippi and O. vulpina Philippi), one of the most widespread Ormiscodes species in Chile and Argentina (Lemaire 2002, Angulo et al 2004), is known to cause severe defoliation of native tree species causing economic losses by killing saplings and reducing timber production, and by decreasing tourism in outbreak areas (Bauerle et al 1997, Baldini & Alvarado 2008). In Chile, where most studies and literature reviews on the biology of Ormiscodes species have been conducted, there are records documenting a significant number of taxonomically diverse hosts for O. amphimone (Table 1). On the contrary, in Argentina, the biology and economic impacts of Ormiscodes species are not well documented (Gentili & Gentili 1988, Giganti et al 1994, Paritsis et al 2009). Here, we present new records of host species for O. amphimone documented in northwestern Patagonia, Argentina, with emphasis on Nothofagus pumilio, which was recently recorded as a host in Chile (Baldini & Alvarado 2008).

Nothofagus pumilio is the most widely distributed species of Nothofagus (the predominant native tree genus in Patagonian forests) in South America, extending from 35º35'S in central Chile to 55º30'S at Cabo de Hornos National Park (Veblen et al 1996, García & Ormazabal 2008). Due to the quality of its wood and the great extent of the resource, N. pumilio is the most important native species for timber production in southern Chile and Argentina (Martínez Pastur et al 2000, Peri et al 2002, Gea-Izquierdo et al 2004).

Given its broad distribution and that it commonly forms monospecific stands, N. pumilio has a surprisingly low number of defoliator species known to reach epidemic levels and cause defoliation. To our knowledge, only four insects are reported to cause severe and extensive defoliation on N. pumilio stands: an unidentified Geometridae-Larentiinae species (Bauerle et al 1997), an unidentified Ormiscodes species (A Holz, T Kizberger, M Mermoz, & S Queiro pers. com.), Ormiscodes amphimone [recently reported in Chile by Baldini & Alvarado (2008)], and Ormiscodes cinammomea (Veblen et al 1996; citing Gentili & Gentili 1988). However, the record of the latter species (i.e. O. cinammomea) as an outbreak species on N. pumilio is uncertain. Larvae of O. amphimone and O. cinammomea are morphologically similar (Bauerle et al 1997, Lemaire 2002); thus, these species may be difficult to differentiate during their larval (the most conspicuous) stage. In addition, records of O. cinammomea as the species responsible for generating severe defoliation on N. pumilio are primarily based on anecdotal observations and apparently not on the identification of adult specimens (Gara et al 1980, Gentili & Gentili 1988, Veblen et al 1996). Finally, multiple publications (including reviews) on Ormiscodes spp. biology do not include N. pumilio as a host for O. cinammomea (Lemaire 2002, Dapoto et al 2003, Baldini & Alvarado 2008). Therefore, the role of O. cinammomea as an outbreak defoliator of N. pumilio is not certain.

On November 2003 we surveyed the vegetation at Paso Puyehue (40º43'S, 71º55'W; 1150 m.a.s.l.; mean annual precipitation circa 3000 mm) in the Nahuel Huapi National Park, searching for Ormiscodes egg clusters and larvae. We found circa 20 unhatched O. amphimone egg clusters on N. pumilio twigs and in subsequent surveys (on December 2003 and January 2004) we also observed multiple groups of O. amphimone larvae feeding on N. pumilio leaves.

We collected egg clusters, 1st and 2nd instar larvae, and we reared these in the laboratory with N. pumilio foliage until adults emerged. The adults were identified as O. amphimone (most likely O. a. amphimone, the typical subspecies) based on descriptions and figures by Lemaire (2002) and by comparison with specimens from collections of the Museo Nacional de Historia Natural in Santiago, Chile, where voucher specimens were deposited. We also found O. amphimone egg clusters and larvae feeding on N. pumilio on subsequent springs and summers (i.e.; 2004, 2005, 2006 and 2007) at the same location. Eggs and larvae were also found on Berberis buxifolia, Escallonia virgata, Nothofagus antarctica, and Ribes magellanica, but less frequently than on N. pumilio (Table 2). In addition to these observations at Paso Puyehue, we also documented the presence of O. amphimone egg clusters on a less mesic site (i.e.; Paso Cordoba, 40º36'S, 71º08'W; 1150 m.a.s.l.; mean annual precipitation circa 1000 mm) on N. pumilio twigs. However, at this xeric site the density of egg clusters was circa one order of magnitude lower than at Paso Puyehue. Larvae hatched from these eggs were also reared until adults emerged.

Although O. amphimone is known to feed on a variety of hosts, including N. pumilio in Chile (Baldini & Alvarado 2008), our record of N. pumilio as a frequent host in our study area is important given the relatively recent and severe Ormiscodes outbreaks on N. pumilio along its latitudinal gradient (Lago Rivadavia, 42º36'S, 71º41'W in 2003 and 2008; Cerro Castillo area, 46º06'S, 72º08'W in 2007, Los Glaciares N.P. 49º20'S, 72º55'W in 1999, 2001, 2003, and 2005). Although all these large and severe defoliations have been attributed to Ormiscodes larvae, the particular species could not be determined. Considering the new evidence provided here and the small number of species documented to severely defoliate N. pumilio, it is likely that all these recent defoliations were generated by O. amphimone larvae. This interpretation is supported by the observation that the only two Ormiscodes species with geographic ranges reaching south of c. 43ºS along the Andes are O. amphimone and O. cognata (Lemaire 2002), and the latter species is not known to experience outbreak events.

The present record of N. pumilio as a host for O. amphimone in the eastern slopes of the Patagonian Andes constitutes an important contribution to the relatively understudied diversity of plant-insect interactions in the Patagonian forests of Argentina. The relevance of this association is reinforced by the ecological, biogeographical, and economical significance of N. pumilio and O. amphimone in this region. In this context, our record provides a foundation for future studies focusing on ecological and biogeographical aspects of this interaction.

Acknowledgments

We would like to thank N. Lescano for lab assistance, M. Béeche for help with specimen identification, T. Kitzberger, M. Mermoz, A. Holz, S. Queiro and M. Berardi for Ormiscodes defoliation records, an anonymous reviewer for useful comments that improved this manuscript, and the Nahuel Huapi National Park Administration for providing the permits for insect collection. This study was partially funded by an NSF Dissertation Improvement Award 0602164 and NSF Award BCS-0117366.

Received 09/II/09.

Accepted 04/V/09.

Edited by Takumasa Kondo - CORPOICA

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Publication Dates

  • Publication in this collection
    17 Jan 2011
  • Date of issue
    Dec 2010

History

  • Accepted
    04 May 2009
  • Received
    09 Feb 2009
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