PS 4-36
Wind as a mode of dispersal for aquatic microinvertebrates in the North American desert southwest
Hydrochory is the typical mode of dispersal for aquatic invertebrates in interconnected watersheds. However, in highly isolated desert playas, wind may be the primary mechanism, facilitating colonization and gene flow among these populations. In the North American desert southwest, dust blows west-to-east, carrying deflated sediments from regional playas. Dormant and resting stages of aquatic invertebrates are carried along across vast distances. Here, we investigate the role of anemochory in dispersing these organisms using two methods: dust sample rehydration and environmental sequencing of dust, sediment, and natural waters from 8 ephemeral wetlands in the Chihuahuan Desert. We collected dust from 14 wind events using Modified Wilson & Cooke collectors from 4 sites near El Paso, TX. Dust samples were split for chemical and biological processing. At least 1 g of dust was rehydrated in artificial hardwater and checked daily for emerging organisms. Wetland water and sediment samples were pooled from each wetland and 3 dust samples, and total DNA was extracted using PowerSoil® and PowerWater® DNA isloation kits. Two sets of universal 18S rRNA primers were used for PCR amplification and sequenced on a MiSeq. In addition, invertebrates hatched from dust samples were sequenced using primers for the mtDNA COI gene.
Results/Conclusions
In 14 rehydrated dust samples, we found a variety of aquatic invertebrates including monogonont (6 species) and bdelloid rotifers, gastrotrichs, nematodes, tardigrades, ostrocods, copepods, and branchiopods. Bdelloid rotifers were most common, occurring in 71% samples. Partial COI sequences show at least 3 species of bdelloids (being confirmed by morphological analyses). Other taxa were rare in samples hydrated thus far. Nematodes were found in three samples (21%) and gastrotrichs and branchiopods in two (14%). These results are not surprising since rotifer diapausing eggs are nearly the same size as the average size of dust particles in our samples (approx. 100 microns) while other taxa tend to have larger resting stages. Preliminary analyses of environmental samples show a diverse array of OTUs. Of these, <1-12% were identified as aquatic invertebrates other than nematodes. Nematodes were prevalent in some sediment and water samples (up to 40%). Of the three dust samples analyzed, sequences identified as arthropods, nematodes, and rotifers were obtained, but with relatively few representative sequences. Both methods demonstrate the regional transport of aquatic invertebrates via wind.