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In the south-eastern United States and globally, increasing human water demand coupled with climate change is diminishing stream flows and increasing stream intermittency in many watersheds. We characterized benthic invertebrate assemblages across a stream flow gradient ranging from intermittent to perennial following a multiyear drought by examining the functional traits that can influence assemblage response to drying. We sampled 13 reaches within the Lower Flint River Basin in south-western Georgia, from September to December 2013. Reaches included perennial, near-perennial (ceased flowing but maintained a wetted channel during drought), intermittent-dry (seasonally dry), and intermittent-frequent (frequently dry). Distinct assemblages were documented across this gradient. Reaches that dried during the drought had a lower richness of aquatic insects, especially Ephemeroptera, Plecoptera, and Trichoptera taxa, partly due to inadequate time for life cycle completion and lack of adaptations to avoid drying.Intermittent reaches also included abundant and unique noninsect taxa such as Gammarus spp.and Isopoda. Projected trends towards increased water demand and drought severity and frequency in the south-eastern United States will magnify shifts towards dominance by drought-tolerant taxa as greater portions of stream networks become intermittent.

Premise of the StudyUnderstanding the phylogenetic distribution of defensive plant secondary metabolites is essential to the macroevolutionary study of chemically mediated plant–animal interactions. The chemical ecology of pyrrolizidine alkaloids (PAs) has been extensively studied in a number of plant–herbivore systems, including Apocynaceae (the milkweed and dogbane family) and Danainae (the milkweed and clearwing butterflies). A systematic survey is necessary to establish a detailed understanding of their occurrence across Apocynaceae. A survey of this species‐rich, mainly tropical and subtropical family will rely heavily on small tissue samples removed from herbarium specimens, some of which will be very old and/or preserved with alcohols or mercuric chloride.MethodsWe optimized PA extraction methods from small leaf fragments of recently collected silica‐dried leaves of the PA‐positive Echites umbellatus, varying crushing and extraction time. We then applied our optimized method to leaf fragments from 70–167‐year‐old herbarium specimens of E. umbellatus. To simulate the effect of alcohol treatment on PA detectability in herbarium specimens, we incubated freshly collected leaves of the PA‐positive Parsonsia alboflavescens in three different alcohols before drying and compared PA recovery to freshly dried controls. PAs were quantified using high‐performance liquid chromatography–mass spectrometry analysis. X‐ray fluorescence was used to identify mercury‐containing specimens.ResultsFifteen seconds of leaf crushing followed by 24 h of extraction were optimal for PA free‐base and N‐oxide recovery. This method yielded ~50‐fold greater PA recovery than prior methods. Half of the herbarium specimens (13 of 23), including the oldest, tested positive for PAs; leaf age did not correlate with success in PA extraction. Treatment of fresh leaves with alcohol before drying did not diminish PA recovery; mercury was observed in both PA‐positive and PA‐negative specimens.Conclusions PAs can be reliably detected in small tissue samples from herbarium specimens up to 167 years old, including specimens that had been treated with alcohol or mercury salts. The variability of PA presence among herbarium specimens of E. umbellatus indicates that multiple specimens will need to be tested before a particular species is determined to lack PAs.

Geographically isolated wetlands (GIWs) are well known as "hotspots" for biodiversity and other ecosystem services, making their value on landscapes disproportionate to the area they occupy. GIWs are dependent on regular cycles of inundation and drying, which makes hydrology a primary controlling variable for sustaining functions and associated ecosystem services. Although human activity has degraded GIWs in many regions, relatively little work has focused on upland management as a way of sustaining, or even improving, GIW structure and function. We present a case study of longleaf pine forest restoration, by hardwood removal, on the characteristics of a wetland hydroperiod over a 10-year study. Our study wetland, W-51, is 0.89 ha with a catchment area of 31.2 ha located on a~11,400-ha private preserve in Baker County, Georgia (31.250°N, 84.495°W). Beginning in 2006, continuous water level and climate data were recorded in the wetland and adjacent well transects across the wetland catchment. In autumn 2009, hardwoods were removed or deadened in the catchment resulting in a 37% reduction in tree cover. The effects on the hydrologic system were measured through 2016 by examining pre-and post-removal water levels, water yield ecosystem (WYe), and standardized recession rates (RR std ). The study included periods of above and below normal rainfall. Generally, wetland hydroperiods began in December and ended in May, but varied with rainfall pattern and amount. Hardwood removal increased WYe and decreased RR std resulting in greater catchment water availability as reflected in water levels. Hardwood removal affected both the ascending and recessing limbs of wetland hydroperiods, substantially increasing the availability of ponded water in the wetland. Our results quantify changes in wetland hydrologic characteristics associated with forest management activities, which appear to have reduced forest water demand. Our study was a management case study, limited in scope but conducted in a realistic setting. More extensive studies (paired, replicated designs) are needed to better understand the implications at both the local scale, that is, managing critical aquatic habitat for wildlife populations, and at the regional scale, that is, providing support for landscape-scale connectivity and water yields.

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Stream intermittency is predicted to increase where water withdrawals and climate warming are increasing. In regions coupled with high fish diversity, understanding how intermittency influences fish trophic ecology is critical for informing ecosystem function. This study compared fish diets across seasons in perennial and intermittent streams to estimate the immediate and cumulative effects of stream drying on fish foraging patterns. We used gut content analysis to compare the diets of small-bodied, secondary consumer fishes, including two minnow and three darter species found in the lower Flint River Basin of southwestern Georgia, during both the summer (before stream dry-down) and fall (post flow resumption) seasons. Fish communities in perennial streams had greater diet richness compared to fishes in intermittent streams for both seasons. Darter diets were characterised by rheophilic aquatic insects in perennial streams and by benthic crustaceans (copepods, cladocerans and isopods) and predatory aquatic insects in intermittent streams. Minnow diets were typified by freshwater sponges, eggs and organic detritus in intermittent streams and by terrestrial insects and diatoms in perennial streams. Fishes in intermittent streams consumed significantly more benthic crustaceans in the fall (37% increase in proportional volume) compared to preflow cessation conditions in the summer, suggesting these organisms play an important, yet relatively unrecognised role in supporting fish communities in southeastern streams. Our findings enhance our understanding of how stream intermittency influences the trophic dynamics of secondary consumer fishes in an agricultural watershed increasingly affected by water scarcity.

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