Macroinvertebrate community structure and biological traits related to flow permanence in a Mediterranean river network

Abstract

In Mediterranean climate areas, the great seasonal variability in temperature and rainfall is considered to be an evolutionary pressure that constrains plant and animal communities and their biological traits. Droughts alter habitat availability (changes of flow alter riffle-pool sequences), although habitat characteristics may also exacerbate drought to some extent. Using a simple quantitative index based on the proportion of conglomerate bedrock versus gravel and cobbles, pools versus riffles and winter versus summer flow, we show how habitat characteristics (in terms of substratum and flow) may influence the permanency of a stream site and how flow permanence constrains macroinvertebrate community structure and biological traits. Annual and seasonal macroinvertebrate richness, and the EPT (Ephemeroptera, Plecoptera and Trichoptera) and OCH (Odonata, Coleoptera and Hemiptera) metrics differed between permanent, intermittent and ephemeral sites, but not between permanent and intermittent sites. In contrast, distinct biological traits were observed in the three flow categories, although permanent sites presented few significant traits which was attributed to the stability of the habitat. Intermittent sites were dominated by taxa with pool-like strategies, while ephemeral sites were characterized by fauna with life-history adaptations to floods and droughts. In contrast to most traits (e.g., dissemination, reproduction, substrate relation), which were more constrained by local flow and substrate characteristics, life-cycle characteristics did not differ significantly among flow categories. This pattern can be explained by the features of the Mediterranean climate and particularly its high seasonal predictability, which serves as a large-scale filter of life-cycle traits, independently of local hydromorphological characteristics. Our findings indicate that drought is related to habitat characteristics and that local habitat variability favours organisms with certain traits, while other traits are independent of habitat variability on this scale and are probably affected by other large-scale habitat characteristics.

Can biological invertebrate traits resolve effects of multiple stressors on running water ecosystems?

“…Using by far fewer stream sites (25 sites, categorised as permanent, intermittent or ephemeral) from Catalonia, Bonada et al (2007b) examined associations between trait categories and discharge temporality …”

Effects of flow events and nutrient addition on stream periphyton and macroinvertebrates: an experimental study using flumes

“…The consequences of natural variation and anthropogenic modifications in flow to riverine biota have been relatively well studied (Rolls et al, 2012;Schneider and Petrin, 2017), and both flow maxima and minima are important. For example, spates can decrease the abundance and diversity of macroinvertebrates (Scrimgeour et al, 1988), but macroinvertebrate assemblages and trait composition are also affected by droughts (Monk et al, 2008;Bonada et al, 2007).…”

Variación temporal de la diversidad taxonómica y rasgos funcionales de los macroinvertebrados acuáticos en ríos temporales en la isla de Providencia, Colombia

“…Una de las estrategias de los insectos para sobrellevar la sequía es el proceso de emerger, así pasan la temporada en el medio terrestre−aéreo. En contraste, se ha encontrado en algunos ríos intermitentes del Mediterráneo que la riqueza de taxones aumenta durante la época de sequía en comparación con la temporada de inundación, esto estaría relacionado con la predictibilidad de la época de sequía en estos ecosistemas y el papel de sistemas intermitentes como zonas de refugio de la fauna de quebradas efímeras (Bogan et al 2015, Bonada et al 2007, Maasri et al 2008, Skoulikidis et al 2017). …”

“…Los rasgos que predominan varían dependiendo de si la sequía es estacional predecible o si es un evento impredecible (Bogan et al 2015, Lake 2003. En general, se ha encontrado en ecosistemas mediterráneos y templados que los rasgos funcionales asociados con mayor adaptación a la temporalidad son: ciclos vitales flexibles (sincronización de los ciclos de vida acuáticos con las temporadas de lluvias), desarrollo ligado con la temperatura del agua, diapausa, huevos protegidos contra la desecación y alto poder de dispersión (Bonada et al 2007, Boulton 1989, Dézerald et al 2015, Dole-Olivier et al 1997, Lake 2003, McDonough et al 2011, Stubbington et al 2016, Williams y Hynes 1977, así como alimentación de tipo generalista (Dieterich y Anderson 2000).…”