Density‐Related Dispersal in Planthoppers: Effects of Interspecific Crowding

Abstract

In dense populations, most planthoppers (Homoptera:Delphacidae) produce fully winged migratory forms that can escape to new habitats. Under less crowded conditions, flightless morphs with reduced wings result. For two sympatric species, Prokelisia marginata and Prokelisia dolus, interspecific crowding was found to be as strong a stimulus for the production of migrants as intraspecific crowding. The effects were reciprocal for both species and were demonstrated both in the laboratory and field. However, because migratory forms were triggered at a much lower density in P. marginata than P. dolus, interspecific interactions were asymmetric, with P. dolus having a far greater influence on the wing form of P. marginata. Interspecific interactions did not directly influence survival, development time, or body size, but reproductive capability was indirectly affected because migratory females are less fecund than their flightless counterparts. Intraspecific crowding adversely affected the survivorship, development time, and body size of P. marginata, but had no influence on the fitness of P. dolus. P. marginata is a much more migratory species than P. dolus. Consequently, mobility is associated with the extent that each species' fitness is reduced by intraspecific crowding. Our results demonstrate that for wing dimorphic insects, the effects of interspecific competition can be extended to include altered wing form, a character that directly influences dispersal capability as well as reproductive potential. We suggest that when wing—dimorphic species share a common habitat, interspecific interactions can influence population dynamics by increasing emigration and decreasing population growth.

Direct and feeding‐induced interactions between two rice planthoppers, Sogatella furcifera and Nilaparvata lugens: effects on dispersal capability and performance

“…Asymmetric effects of interspecific crowding on wing form have been reported in other studies involving planthoppers (Prokelisia species) in which one species triggered macroptery selectively in the other (Denno & Roderick, 1992). In this study, macropters were produced by the inferior competitor (Prokelisia marginata), which suffered reduced survival and extended development in the presence of the competitive dominant (Prokelisia dolus) (Denno & Roderick, 1992;Denno et al, 2000). Similarly, in the present study, macropters were produced in female N. lugens in the presence of S. furcifera (Fig.…”

“…For example, dispersal capability in flight-dimorphic insects is influenced by various environmental cues such as crowding and host plant condition, temperature, and photoperiod (Harrison, 1980;Roff, 1986;Zera & Denno, 1997). Among these environmental cues, crowding and its interaction with plant quality are thought to be the most influential factors in many insect species, including most delphacid planthoppers (Kisimoto, 1965;Denno et al, 1994;Matsumura, 1996a), however previous studies involving planthoppers and other insects have focused almost entirely on the effects of intraspecific crowding on wing-form determination (Kisimoto, 1965;Morooka et al, 1988;Matsumura, 1996a; but see Denno & Roderick, 1992). This study showed clearly that interspecific crowding also has strong effects on wingform determination and thus dispersal capability in two rice-inhabiting planthopper species, S. furcifera and N. lugens.…”

“…In most species (e.g. many crickets and planthoppers), wing-form determination results from a combination of genetic and environmental factors (Roff, 1986;Denno & Roderick, 1992;Matsumura, 1996a;Zera & Denno, 1997). Thus, wing form is determined by an environmentally sensitive switch that specifies the development of either a macropter or a brachypter (Harrison, 1980;Roff, 1986;Roff & Fairbairn, 1991;Matsumura, 1996a;Zera & Denno, 1997).…”

“…Thus, wing form is determined by an environmentally sensitive switch that specifies the development of either a macropter or a brachypter (Harrison, 1980;Roff, 1986;Roff & Fairbairn, 1991;Matsumura, 1996a;Zera & Denno, 1997). Various environmental cues such as intraspecific crowding, host plant nutrition, temperature, and photoperiod influence wing-form determination (Harrison, 1980;Zera & Denno, 1997), however the effect of interspecific crowding on wingform determination has been studied poorly in most insect herbivores (but see Lamb & MacKay, 1987;Denno & Roderick, 1992;Denno et al, 2000).…”

Biodiversity, Habitat Area, Resource Growth Rate and Interference Competition

“…Direct interference resulting in mortality for three species of consumers. In the top figure, survivorship of planthoppers decreases with increasing density due to the effects of intraspecific interference mediated indirectly via plant tissue quality [redrawn from Denno and Roderick (1992)]. In the middle figure, the adults of the whitefly parasitioid Encarsia sophia engage in 'host feeding' [redrawn from Jervis and Kidd (1986)], killing conspecific juveniles when they attack previously parasitized whitefly hosts (Collier and Hunter, 2001).…”