Young limnologists link functional ecology and invasive species habitat niches to predict biodiversity losses
Version in Spanish and Portuguese
Biological
invasions are one of the most important causes of biodiversity loss and
ecosystem change worldwide, which are especially damaging in aquatic habitats.
However, it is still unclear how biological invasions may interact with local
abiotic stressors (e.g., salinity, land-use intensification), which are
expected to increase as global change intensifies. Furthermore, we know little
about the response of native communities of insects to biological invasions,
despite the huge contribution of insects to global animal biodiversity,
especially in freshwater ecosystems.
So far, the study of the
invasiveness of alien species has been focused mainly on isolated biological
characteristics (e.g. body size, trophic strategy) and the specific ecosystem
impacts induced by alien species. Yet it remains unclear how the ecological and
biological similarity between native and alien species may influence the
success and the impact of biological invasions, especially in the presence of
intense environmental stressors.
In a new study recently published in Functional Ecology, we investigated the
impact of an invasive water boatman (Trichocorixa verticalis verticalis) on
the co-existence patterns of three native boatman Sigara species (Sigara lateralis, Sigara scripta and Sigara
selecta) along a salinity gradient. Trichocorixa
verticalis verticalis, originally distributed in North America and the
Caribbean, has been recorded as an alien species in South Africa, New
Caledonia, Morocco, Spain and Portugal, being the only water bug recognised as
an alien species in Europe.
Fig. 1. The alien species Trichocorixa verticalis verticalis
In our study, we characterised
the habitat specialisation and functional niches of each species from
physiological and biological characteristics, respectively, and their degree of
overlap. The physiological characteristic studied was the salinity tolerance of
the different life stages (eggs, nymphs and adults) of each species. On the
other hand, the biological characteristics selected were fecundity, dispersal
ability, feeding strategy, life cycle and size.
Fig 2. One of
the surveyed wetlands at the Doñana National Park (Spain)
After characterising the
habitat specialisation and functional niches, we used field data (salinity and
species presence) to compare the coexistence patterns of native and invasive
species in invaded (south-western Iberia and northern Morocco) and non-invaded (south-eastern
Iberia) areas.
Finally, we tested if habitat
filtering (stress gradient segregates species into different habitats allowing
regional coexistence) or niche differentiation (different resource exploitation
allows the coexistence of species) assembly rules mediate their coexistence. To
carry this out, we tested the actual co-occurrence values against the patterns
found in simulated matrices created under null model scenarios of
habitat filtering and niche differentiation.
Fig. 3. The three native boatman species. A) Sigara lateralis, B) Sigara scripta, C) Sigara selecta
Our results showed that the
presence of the invasive insect modifies the distribution and coexistence
patterns of native boatmen. We found that in non-invaded areas habitat
filtering drives habitat segregation of the native species along the salinity
gradient, with a lower contribution of niche differentiation. On the other
hand, in invaded areas niche differentiation seems to be the main mechanism
preventing competition among the invasive and native species, enabling
coexistence and resource partitioning along the salinity gradient.
The present work makes a novel contribution to the study of the impacts
of invasive species at the community level by integrating habitat
specialisation and functional niche approaches with field occurrence data. We
showed how the presence of the invasive species T. v. verticalis can modify the distribution and co-occurrence
patterns of native Sigara species
along the salinity gradient, as well as the main assembly rules that shape the
assemblages in non-invaded and invaded areas. Our approach can also be useful
to anticipate the consequences of ecologically novel invaders for native
communities at structural and functional levels under a global change context.
Fig. 4. José
Antonio Carbonell collecting macroinvertebrate samples
Carbonell, J. A.,
Velasco, J., Millán, A., Green, A. J., Coccia, C., Guareschi, S., &
Gutiérrez-Cánovas, C. (2017). Biological
invasion modifies the co-occurrence patterns of insects along a stress gradient. Functional
Ecology. DOI: 10.1111/1365-2435.12884.
