Quantitative Genetics, Development, and Physiological Adaptation in Host Strains of Fall Armyworm

Pashley, Dorothy P.

doi:10.1111/j.1558-5646.1988.tb04110.x

Cited by 85 publications

(52 citation statements)

References 47 publications

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“…Theory suggests that populations can diverge even when in contact with each other (Endler 1977;Felsenstein 1981;Rice 1987;Gavrilets et al 2000). Moreover, there are numerous examples of populations that appear to be diverging, presumably because of differences in habitat or resource use (Pashley 1988;Feder et al 1989;Brown et al 1996;Wood and Foote 1996;Carroll et al 1997;McMillan et al 1997;Hatfield and Schluter 1999;Lu and Bernatchez 1999;Via 1999).…”

Section: Discussionmentioning

confidence: 99%

How Fluctuating Competition and Phenotypic Plasticity Mediate Species Divergence

2002

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Causal evidence linking resource competition to species divergence is scarce. In this study, we coupled field observations with experiments to ask if the degree of character displacement reflects the intensity of competition between two closely related spadefoot toads (Spea bombifrons and S. multiplicata). Tadpoles of both species develop into either a small-headed omnivorous morph, which feeds mostly on detritus, or a large-headed carnivorous morph, which specializes on and whose phenotype is induced by fairy shrimp. Previously, we found that S. multiplicata are inferior competitors for fairy shrimp and are less likely to develop into carnivores in sympatry with S. bombifrons. We compared four key trophic characters in S. multiplicata across natural ponds where the frequency of S. bombifrons varied. We found that S. multiplicata became increasingly more omnivore-like as the relative abundance of S. bombifrons increased. Moreover, in controlled laboratory populations, S. multiplicata became increasingly more omnivore-like and S. bombifrons became increasingly more carnivore-like as we increased the relative abundance of the other species. Phenotypic plasticity helped mediate this divergence: S. multiplicata became increasingly less likely to eat shrimp and develop into carnivores in the presence of S. bombifrons, a superior predator on shrimp. However, divergence also reflected differences in canalized traits: When reared under common conditions, S. multiplicata tadpoles became increasingly less likely to produce carnivores as their natal pond decreased in elevation. Presumably, this pattern reflected selection against carnivores in lower-elevation ponds, because S. bombifrons became increasingly more common with decreasing elevation. Local genetic adaptation to the presence of S. bombifrons was remarkably fine grained, with differences in carnivore production detected between populations a few kilometers apart. Our results suggest that the degree of character displacement potentially reflects the intensity of competition between interacting species and that both phenotypic plasticity and fine-scale genetic differentiation can mediate this response. Moreover, these results provide causal evidence linking resource competition to species divergence.

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Section: Discussionmentioning

confidence: 99%

How Fluctuating Competition and Phenotypic Plasticity Mediate Species Divergence

2002

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“…In terms of larval performance, the rice strain was found to develop better on rice plants than on corn plants, while the corn strain performed equally well on both plants (Pencoe and Martin 1981, Pashley 1988, Whitford 1988, Pashley et al 1995. Conversely, in nature the corn strain seems to be more restricted to corn habitats and is rarely found in rice habitats, while the rice strain can be found on corn as well (Pashley et al 1995).…”

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confidence: 90%

“…The strains have been reported to exhibit mechanisms of reproductive isolation, developmental and physiological variations, and genetic polymorphisms (Pashley 1986(Pashley , 1988Pashley and Martin 1987;Whitford et al 1988;Quisenberry 1991;Pashley et al 1995;Adamczyk et al 1997;McMichael and Prowell 1999;Nagoshi and Meagher, 2004;Groot et al 2010). However, the results from different studies, which in some cases included hybrid progeny, were not always consistent, with no physiological or behavioral studies under laboratory conditions being able to distinguish between the two strains.…”

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confidence: 99%

Host Association of Spodoptera frugiperda (Lepidoptera: Noctuidae) Corn and Rice Strains in Argentina, Brazil, and Paraguay

Juárez

Murúa

García³

et al. 2012

jnl. econ. entom.

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Spodoptera frugiperda (J.E. Smith) is composed of two genetically distinct strains, the so-called corn strain and the rice strain. Whether the two strains differ in their host use is unclear, because laboratory experiments have not been able to show consistent host performance or preference differences between them, and field studies showed high rates of hybridization, as well as some degree asymmetric host use. To determine the distribution of the two strains and their association with host plants, we collected fall armyworm larvae from different crops (corn, rice, alfalfa, and sorghum) and grasses in 15 different localities over 4 yr in Argentina, Brazil, and Paraguay. The strain identity was analyzed using two polymorphisms in the mitochondrial cytochrome oxidase subunit I gene. We identified the corn and rice haplotypes and three types of populations were characterized based on the frequencies of the individuals that belonged to any of these haplotypes: in 44% of populations the corn haplotype predominated, in 44% of populations the rice haplotype was the most frequent, and 11% of populations showed both haplotypes at similar proportions. In total, eight populations (47%) showed the expected pattern, two populations (12%) were polymorphic within the same field, and seven populations (41%) showed the inverse pattern. Taken together, there was no consistent pattern of host association between the two sympatric genotypes and their respective host plants. This investigation supports the need for additional studies to determine which other forces keep the genotypes separate, and what is the degree of genetic differentiation between these populations.

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“…These two host forms exhibit some degree of reproductive isolation, including (1) ecological isolation caused by differential use of host plants (Pashley, 1986(Pashley, , 1988aProwell et al, 2004), larval performance differences (Pencoe & Martin, 1981;Pashley, 1988b;Whitford et al, 1988;Pashley et al, 1995), and oviposition preference (Whitford et al, 1988;Meagher et al, 2011); (2) temporal isolation caused by temporal partitioning of nocturnal mating activities (Pashley et al, 1992;Sch€ ofl et al, 2009); (3) female-mediated differential mating preferences (Sch€ ofl et al, 2011); and (4) potential sexual isolation caused by differences in the composition of female sex pheromones (Groot et al, 2008;Lima & McNeil, 2009) and directionally biased incompatibility and low viability in hybrids (Pashley & Martin, 1987;Whitford et al, 1988;Groot et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

Population structure of Spodoptera frugiperda maize and rice host forms in South America: are they host strains?

Juárez

Schöfl

Vera

et al. 2014

Entomologia Exp Applicata

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Determining which factors contribute to the formation and maintenance of genetic divergence to evaluate their relative importance as a cause of biological differentiation is among the major challenges in evolutionary biology. In Spodoptera frugiperda (Smith) (Lepidoptera: Noctuidae) two host strains have been recognized in the 1980s: the corn‐strain prefers maize, sorghum, and cotton, whereas the rice‐strain prefers rice and wild grasses. However, it is not clear to what extent these so‐called ‘strains’, which have also been called ‘host races’ or even ‘sibling species’, are really associated with host plants. Due to the indeterminate evolutionary status, we will use the term ‘host forms’ (sensu Funk). Here, we characterized populations collected from maize, rice, and wild grasses from three countries in South America. Using two mitochondrial cytochrome oxidase I (mtCOI) markers and 10 polymorphisms in the triose phosphate isomerase (Tpi) gene, we found various patterns of host association. Two hundred twenty‐seven nuclear amplified fragment length polymorphisms (AFLPs) markers revealed significant genetic differentiation among populations, which was generally correlated to the host from which the larvae were collected. Using a multivariate discriminant analysis and a Bayesian clustering approach, we found that individuals could be grouped into 2–5 genetically distinct clusters, depending on the method. Together, our results indicate that although host‐associated differentiation is present in this species, it does not account for all observable genetic variation and other factors must be maintaining genetic differentiation between these forms. Therefore, the term ‘host strains’ should be abandoned and ‘host forms’ should be used instead for S. frugiperda.

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Quantitative Genetics, Development, and Physiological Adaptation in Host Strains of Fall Armyworm

Cited by 85 publications

References 47 publications

How Fluctuating Competition and Phenotypic Plasticity Mediate Species Divergence

How Fluctuating Competition and Phenotypic Plasticity Mediate Species Divergence

Host Association of Spodoptera frugiperda (Lepidoptera: Noctuidae) Corn and Rice Strains in Argentina, Brazil, and Paraguay

Population structure of Spodoptera frugiperda maize and rice host forms in South America: are they host strains?

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