Temperature-Specific Competition between Invasive Mosquitofish and an Endangered Cyprinodontid Fish

Abstract

Condition-specific competition is widespread in nature. Species inhabiting heterogeneous environments tend to differ in competitive abilities depending on environmental stressors. Interactions between these factors can allow coexistence of competing species, which may be particularly important between invasive and native species. Here, we examine the effects of temperature on competitive interactions between invasive mosquitofish, Gambusia holbrooki, and an endemic Iberian toothcarp, Aphanius iberus. We compare the tendency to approach heterospecifics and food capture rates between these two species, and examine differences between sexes and species in aggressive interactions, at three different temperatures (19, 24 and 29°C) in three laboratory experiments. Mosquitofish exhibit much more aggression than toothcarp. We show that mosquitofish have the capacity to competitively displace toothcarp through interference competition and this outcome is more likely at higher temperatures. We also show a reversal in the competitive hierarchy through reduced food capture rate by mosquitofish at lower temperatures and suggest that these two types of competition may act synergistically to deprive toothcarp of food at higher temperatures. Males of both species carry out more overtly aggressive acts than females, which is probably related to the marked sexual dimorphism and associated mating systems of these two species. Mosquitofish may thus impact heavily on toothcarp, and competition from mosquitofish, especially in warmer summer months, may lead to changes in abundance of the native species and displacement to non-preferred habitats. Globally increasing temperatures mean that highly invasive, warm-water mosquitofish may be able to colonize environments from which they are currently excluded through reduced physiological tolerance to low temperatures. Research into the effects of temperature on interactions between native and invasive species is thus of fundamental importance.

Temporal genetic dynamics among mosquitofish (Gambusia holbrooki) populations in invaded watersheds

“…A year later, a few hundred individuals from their offspring were transplanted to Italy (reviewed in NavarroGarcıa, 2013) and from there to every other European and Mediterranean country in the following years (Sholdt et al, 1972). Introduced mosquitofish are now playing a key role in Spanish Mediterranean freshwater ecosystems by competing and displacing endemic fish species such as the Spanish toothcarp, Aphanius iberus, and the Valencia toothcarp, Valencia hispanica (Rincon et al, 2002;Alcaraz et al, 2008;Carmona-Catot et al, 2013). The reduced genetic variation in mtDNA among European G. holbrooki populations supports the abovementioned historical records confirming a common source for the majority of these populations and indicates a notorious uniformity among Iberian populations (Vidal et al, 2010).…”

Ecological impact of inland fish introduced to the Iberian Peninsula

“…La gambusia se introdujo en Europa a través de España en 1921 (Vidal et al 2010) y es una de los peces más invasores de las aguas continentales mediterráneas y del mundo en general (Lowe et al 2000). La gambusia es una especie agresiva y a menudo muy abundante durante los meses cálidos (Meffe y Snelson 1989;Evans et al 2011) y seguramente es la especie de pez de la que mejor se conoce el impacto ecológico en la península (Carmona-Catot et al 2013). …”

“…La mayoría de estudios han encontrado considerable agresión de gambusia hacia los ciprinodontiformes nativos (Rincón et al 2002;Alcaraz et al 2008;Carmona-Catot et al 2013); el único estudio que no halló tal agresión (Caiola y de Sostoa 2005) usaba densidades muy bajas. La gambusia también afecta a las especies nativas por depredación en juveniles de otras especies (aunque esto es difícil de demostrar) y por competencia por los recursos.…”

“…La gambusia también afecta a las especies nativas por depredación en juveniles de otras especies (aunque esto es difícil de demostrar) y por competencia por los recursos. La gambusia se muestra a menudo más voraz que las especies nativas (Alcaraz et al 2008;Carmona-Catot et al 2013) y disminuye la tasa de alimentación de estas (Rincón et al 2002), incluso cuando las nativas son más abundantes y los recursos alimentarios no son limitantes (Caiola y de Sostoa 2005). Sin embargo, la competencia entre gambusia y los peces nativos depende claramente de los factores ambientales (condition-specific or contex-dependent competition).…”

“…Sin embargo, la competencia entre gambusia y los peces nativos depende claramente de los factores ambientales (condition-specific or contex-dependent competition). La gambusia es menos eficiente y agresiva a bajas temperaturas (Rincón et al 2002;Carmona-Catot et al 2013) y altas salinidades (Alcaraz y García-Berthou 2007;Alcaraz et al 2008). Como el fartet básicamente se encuentra actualmente en lagunas costeras muy fluctuantes en salinidad pero a menudo hipersalinas en verano, estos hábitats pueden proporcionar un refugio competitivo respecto la gambusia (Alcaraz y García-Berthou 2007;Alcaraz et al 2008;CarmonaCatot et al 2013).…”