Urbanization Impacts the Taxonomic and Functional Structure of Aquatic Macroinvertebrate Communities in a Small Neotropical City
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Urban Ecosyst DOI 10.1007/s11252-017-0653-6 Urbanization impacts the taxonomic and functional structure of aquatic macroinvertebrate communities in a small Neotropical city Stanislas Talaga1,2 & Olivier Dézerald2 & Alexis Carteron2 & Céline Leroy3 & Jean-François Carrias4 & Régis Céréghino5 & Alain Dejean2,5 # Springer Science+Business Media New York 2017 Abstract Due to habitat fragmentation, resource disruption were negatively affected. Because we cannot ascertain wheth- and pollution, urbanization is one of the most destructive er the decline in filter-feeders is related to food web-mediated forms of anthropization affecting ecosystems worldwide. effects or to competitive exclusion (Aedes aegypti mosquitoes Generally, human-mediated perturbations dramatically alter were present in urban bromeliads only), further studies are species diversity in urban sites compared to the surroundings, necessary to account for the effects of intra-guild competition thus influencing the functioning of the entire ecosystem. We or inter-guild facilitation. investigated the taxonomic and functional diversity patterns of the aquatic macroinvertebrate communities in tank bromeliads Keywords Aedes aegypti . Bioindicator . Diversity . by comparing those found in a small Neotropical city with Functional traits . Tank bromeliads . Urban ecology those from an adjacent rural site. Changes in the quality of detrital inputs in relation to lower tree diversity and the pres- ence of synanthropic species are likely important driving Introduction forces behind the observed structural changes in the urban site. Leaf-litter processors (i.e., shredders, scrapers) were positive- Urbanization is one of the most destructive forms of anthro- ly affected in the urban site, while filter-feeders that process pogenic disturbance experienced by ecosystems worldwide. smaller particles produced by the activity of the shredders Generally, species diversity is altered dramatically in urban sites compared to the surroundings. The loss of natural habitat, habitat fragmentation, resource disruption and pollution are Electronic supplementary material The online version of this article (doi:10.1007/s11252-017-0653-6) contains supplementary material, among the main causes; moreover, urban areas are hotter which is available to authorized users. and drier than rural ones (‘urban heat island effect’)because the vegetation is supplanted by impervious surfaces, reducing * Stanislas Talaga evaporation and evapotranspiration (McKinney 2002, 2008). [email protected] Also, the greater density of artificial, man-made habitats (e.g., ponds, domestic gardens) fosters colonization by either native 1 Institut Pasteur de la Guyane, Unité d’Entomologie Médicale, 23 or synanthropic species (Santoul et al. 2009; Talaga et al. Avenue Pasteur, BP 6010, 97306 Cayenne cedex, France 2015). 2 CNRS, UMR EcoFoG, AgroParisTech, Cirad, INRA, Université des Even if the presence and abundance of most species are Antilles, Université de Guyane, 97310 Kourou, France influenced by urbanization, community-level responses can- 3 IRD, UMR AMAP, Cirad, CNRS, INRA, Université de Montpellier, not only be interpreted as a simplification equivalent to a Boulevard de la Lironde, TA A-51/PS2, cedex 5, decrease in α diversity (McIntyre 2000). Indeed, the negative 34398 Montpellier, France or positive effects of urbanization upon community diversity 4 Université Clermont Auvergne, CNRS, LMGE, differ markedly between taxonomic groups, and explanations 63000 Clermont-Ferrand, France for the contrasting patterns lie in the nature of the processes 5 Ecolab, Université de Toulouse, CNRS, INPT, UPS, acting on the focal taxa studied (Henle et al. 2004). For exam- 31400 Toulouse, France ple, the habitat fragmentation inherent to urban areas Urban Ecosyst adversely affects vertebrates due to gene flow disruption be- investigated the influence of urbanization on the macroinver- tween populations (Delaney et al. 2010), whereas inverte- tebrate communities living in the tanks of an abundant brome- brates are less affected given the small habitat size needed to liad species by comparing their biodiversity, and taxonomic sustain a population (Jones and Leather 2013). Moreover, a and functional structure between an urban and a rural site higher β diversity can be detected within urban areas where using a small Neotropical city as a model. We also verified habitat fragmentation increases habitat heterogeneity, pro- if urbanization favors the presence of synanthropic and/or ex- motes edge species, and/or creates specific niches for inverte- otic species. brates (Jones and Leather 2013). In the Neotropics, tank bromeliads form a highly discon- tinuous aquatic meta-habitat embedded within a terrestrial ma- Materials and methods trix. These phytotelmata (‘plant-held waters’)provideahabi- tat to aquatic organisms ranging from bacteria to small verte- Study area brates (Kitching 2000; Brouard et al. 2012). Interestingly, this spatially discrete microecosystem can be sampled exhaustive- This study was conducted in the coastal region of French ly, providing unbiased records of community-level diversity Guiana, in and around the city of Sinnamary (05°22′39″N and a relevant model system to bring out environmental ef- 52°57′35″W) during the 2011 dry season. The area has an fects on community assembly (Srivastava et al. 2004). The equatorial monsoon climate corresponding to an average of key environmental determinants structuring aquatic macroin- 2800 mm of yearly rainfall distributed over 251 days (Peel vertebrate communities in tank bromeliads are related to the et al. 2007). There is a major drop in rainfall from mid-July characteristics of the aquatic compartment (i.e., habitat size to mid-November (dry season) and a shorter and more irreg- and complexity, food resources, presence of a top predator) ular dry period in March. Minimum and maximum monthly and to the characteristics of the terrestrial matrix most often mean temperatures, relatively stable, vary between 23.6 °C evaluated as open versus closed environments (Brouard et al. and 31.6 °C. 2012;Dézeraldetal.2013, 2014, 2017; Hammill et al. 2015; The residential urban area of Sinnamary, which is home to Trzcinski et al. 2016). Tank bromeliads are common epiphytes most of the 3165 inhabitants recorded within the municipality in Neotropical cities where the structure of their aquatic com- (INSEE 2012), displays a moderate level of urbanization rep- munities can be directly or indirectly influenced by human- resentative of a common form of urbanization in the mediated pressures (Talaga et al. 2015). The fragmentation of Neotropics. In an attempt to control the proliferation of adult the terrestrial matrix caused by urbanization clearly increases Aedes aegypti (Linnaeus 1762), a well-known mosquito vec- the patchy distribution of trees and, so, that of the epiphytes tor of chikungunya, dengue and zika (Christophers 1960), the they host. Consequently, their aquatic compartment might be city of Sinnamary is ULV-sprayed during selected periods directly affected by less tree canopy cover that leads to a with different insecticide. This was the case throughout the reduction in incoming detritus (e.g., leaf litter) and to an in- sampling period during which each street of the city were crease in incident radiation, whereas the characteristics of the sprayed weekly with a solution of 1 g of deltamethrin (Aqua terrestrial matrix negatively impact their colonization. Indeed, K-Othrine®, Bayer, Leverkusen, Germany) per hectare most macroinvertebrates developing in the tanks of brome- (Centre de démoustication de Sinnamary, personal liads are larvae with winged, terrestrial adults that are active communication). dispersers whose range of activity can be limited in the hotter Impervious surface areas were calculated within the con- and drier conditions of urban areas (passive dispersers like vex hulls formed by the A. aquilega sampled at each site using worms and crustaceans colonize new aquatic habitats through QGIS software (QGIS Development Team 2015). The per- phoresy). centages of impervious surface areas were 14.23% and Most studies on urban ecosystems have been conducted in 47.59% in the rural and urban sites, respectively, falling into temperate regions in Europe and North America. Those con- the low (< 20% impervious surface area) and moderate (20– ducted in the Tropics were mostly confined to megacities that 50% impervious surface area) categories proposed by are not very different from their temperate counterparts in McKinney (2002). terms of landscape features. Yet, most tropical urban areas are represented by medium to small urban settlements The focal plant taxa and sampling methods displaying comparatively low levels of urbanization and are often adjacent to natural habitats (Savard et al. 2000;Grau In this region, the tank bromeliad Aechmea aquilega (Salisb.) et al. 2008). Consequently, a reduction in the range of the Griseb. naturally occurs along a gradient of anthropogenic natural-to-urban gradient is likely to favor exchanges between disturbance from rural to urban areas. This bromeliad abounds the two environments and thus limit the influence of urbani- on medium to large trees, either native or exotic species, and zation on communities. To test this hypothesis, we mainly comprised of mango trees in the city of Sinnamary Urban Ecosyst (Talaga et al. 2015). We sampled 26 mature A. aquilega on other families were identified using Merritt and Cummins’ trees at two sites (13 individuals