Aquatic Macrophyte Vegetation Promotes Taxonomic and Functional Diversity of Odonata Assemblages in Intermittent Karst Rivers in the Mediterranean

Abstract

Assemblages of adult Odonata were studied in four intermittent karst rivers encompassing macrophyte-rich (MRH) and macrophyte-poor habitats (MPH) in southern Europe, where temporary lotic habitats are the predominant freshwater type but are still understudied. With a total of 25 recorded species, the studied habitats support species-rich Odonata assemblages, as already shown for intermittent rivers in the Mediterranean. Aquatic macrophyte abundance, conductivity, and water velocity are the most significant determinants of Odonata assemblages in the studied IRES. MRH promote higher Odonata abundance and the taxonomic and functional diversity of their assemblages compared to the MPH. Odonata assemblages in MRH are characterized by higher values of body size and a higher share of species preferring lentic and temporary hydrological conditions. Moreover, their assemblages are characterized by various patterns of nymphal development and drought resilience strategies. In contrast, MPH are preferred by lotic species, with nymphal development all year round and with no specific drought-resisting strategies. Our results contribute to the knowledge of diversity and ecological requirements of dragonflies and damselflies in IRES habitats, which could provide scientific background for future conservation activities and bioassessment protocols of such habitats and their biota.

Odonata Assemblages as a Tool to Assess the Conservation Value of Intermittent Rivers in the Mediterranean

“…Our results clearly show that intermittent rivers in the Mediterranean harbor speciesrich Odonata assemblages (see also [42]), as already presented by several studies (e.g., [42,[84][85][86]). Many Odonata species have specific life-history adaptations enabling them to inhabit extreme temporary habitats, for instance, desiccation-tolerant eggs [40,87,88] or rapid nymphal development allowing for their emergence before the habitat dries out [89].…”

“…The results of this study show that among the four studied Mediterranean intermittent rivers, higher Odonata species richness and conservation values were associated with the rivers characterized by higher land-cover heterogeneity, i.e., the Miljašić Jaruga and Čikola rivers. The high number of different land-cover classes in the catchments of those rivers likely increases overall habitat heterogeneity, which is reflected through well-developed aquatic (submerged, emergent, floating) [ 42 ] and riparian vegetation. Interestingly, many of the land-cover classes surrounding the Miljašić Jaruga and Čikola rivers are of anthropogenic origin.…”

“…The study sites along each river differ in aquatic and riparian vegetation structure, microhabitat composition, and physico-chemical water properties [ 42 ], influencing the recorded differences in the composition and abundance of Odonata species. Several authors suggested that in order to assess total Odonata species richness and its relationship with a particular habitat, all phases of the life cycle must be included in the study, i.e., nymphs, exuviae, and adults (see in [ 55 ]).…”

“…The average annual air temperature is around 14 °C, and the average annual precipitation is about 1000 mm [53]. In the course of the study, three sites were visited at each of the four rivers and in three sampling occasions: the first site was closest to the river source, while the third was the farthest (Appendix A Table A1, Figures 1 and 2) (see also [42]). (d-f) study sites 1-3 at the Miljašić Jaruga River.…”

“…Numerous extant Odonata species are generalists, but many of them are also highly specialized, sensitive to change in both aquatic and terrestrial habitat conditions [ 35 , 36 , 37 ]. Previous studies showed that bottom substrate, submerged aquatic vegetation and water clarity are among the most important habitat characteristics for Odonata nymphs, while habitat selection in adults primarily depends on habitat structural heterogeneity, which includes aquatic and riparian vegetation structure and shading [ 38 , 39 , 40 , 41 , 42 ].…”