Knocking back invasions: variable resistance and resilience to multiple cold spells in native vs. nonnative fishes

Abstract

Extreme climate events can interact synergistically with invasions to dramatically alter ecosystem structure, function, and services. Yet, the effects of extreme climate events on species invasions remain unresolved. Extreme climate events may increase resources and decrease biotic resistance by causing physiological stress and/or mortality of native taxa, resulting in invasion opportunities for nonnative species. Alternatively, extreme climate events may regulate nonnative populations, preventing them from achieving dominance. We examined whether a sequence of three cold spells had a negative or positive effect on fish invasions in the coastal Everglades. We compared resistance (initial effects) and resilience (rate of recovery) to the cold spells between native fishes and the dominant nonnative invader, the Mayan cichlid, across eight populations expanding two mangroves drainages in the southern Everglades. We tracked native fish and nonnative Mayan cichlid populations for 10 yr including 3 yr pre‐ and 4 yr post‐cold spells. In both drainages, native fishes were more resistant to the cold spells than the nonnative species. While native fishes experienced declines at only one site, nonnative Mayan numbers were reduced by 90–100% across six sites where they were abundant pre‐disturbances. Four years after the last cold spell, we saw limited resilience in the affected nonnative populations. Only one of the six affected sites fully recovered, whereas the other five sites showed no recovery in Mayan cichlid numbers. The recovered site was closest to a canal, known to act as thermal refuges for nonnative fishes. In summary, cold spells can reduce nonnative abundances, but whether cold spells can effectively knock back invasions (and range expansions) by tropical/subtropical nonnative species will depend on how the frequency and severity of cold spells are affected by climate change. We propose that these mortality‐causing extreme events could provide rare management opportunities late in an invasion.

Lower Lethal Temperatures for Nonnative Freshwater Fishes in Everglades National Park, Florida

“…() and in additional headwater mangrove creeks in Everglades National Park (Boucek and Rehage ; Rehage et al. ). Although cold‐induced mortality may moderate some of the ecological impacts by temporarily reducing population sizes of abundant nonnative fishes, these studies also demonstrate the variability of nonnative fish populations that results from their cold intolerance.…”

Investigating Sub-tropical Community Resistance and Resilience to Climate Disturbance

“…Rehage et al (2016) attribute this spatial variation in resilience to differences in distance to warm water source populations. Likewise, Stevens et al (2016) found that following the 2010 cold spell in Florida, resistance of a tropical estuarine piscivore were similar across three of four estuaries but resilience varied, possibly an effect related to inter-estuary differences in geophysical structuring that may influence reproduction, recruitment, and juvenile survival.…”

“…For instance, Rehage et al (2016) showed that across eight non-native fish populations affected by the 2010 disturbance, population resilience varied from within one year, to populations that have exhibited no recovery five years post disturbance. Rehage et al (2016) attribute this spatial variation in resilience to differences in distance to warm water source populations.…”

“…Similarly, bamboo fields planted with non-native species suffered greater losses than fields seeded with native bamboo following the 2008 cold event (Junming et al 2008;Zhou et al 2011). In Florida, Boucek and Rehage (2014) and Rehage et al (2016) found that tropical native fishes were both more resistant and resilient to extreme cold compared to their functionally similar nonnative counter parts. Similarly, Downing et al (2016) found that non-native bees in subtropical Florida were less resistant to the 2010 cold spell than native bees.…”

Consequences of Anthropogenic and Global Change on Orchids: An Emphasis on Biotic Interactions

“…Over the long-term, extreme cold spells contribute to the physiological threshold ranges for native species, and in theory can limit the range expansions of some introduced species. With cold tolerances being one of the main determinants for a species distributional range, there is a chance for the population decline of a non-native species in the event of an extreme climatic event, such as a cold spell (Kreyling et al 2015, Rehage et al 2015. As a result, measuring species' responses to extreme events in addition to the mean changes in climate is necessary to predict species range limits under future conditions (Zimmerman et al 2009).…”