Predation on Live and Artificial Insect Prey Shows Different Global Latitudinal Patterns

AimLong-standing theory predicts that the intensity of biotic interactions increases from high to low latitudes. Studies addressing geographic variation in predation on insect prey have often relied on prey models, which lack many characteristics of live prey. Our goals were to explore global latitudinal patterns of predator attack rates on standardised live insect prey and to compare the patterns in predation on live insects with those on plasticine prey models.LocationGlobal forested areas.Time Period2021–2023.Major TaxaArthropods, birds.MethodsWe measured predation rates in 43 forested locations distributed across five continents from 34.1° S to 69.5° N latitude. At each location, we exposed 20 sets of three bait types, one set per tree. Each set included three live fly larvae (maggots), three live fly puparia and three plasticine models of the puparia. We used glue rings to isolate half of the sets from non-flying predators.ResultsArthropod attack rates on plasticine prey decreased linearly from low to high latitudes, whereas attack rates on maggots had a U shaped distribution, with the lowest predation rates at temperate latitudes and the highest rates at tropical and boreal latitudes. This difference emerged from intensive predator attacks on live maggots, but not on plasticine models, in boreal sites. Site-specific attack rates of arthropod predators on live and plasticine prey were not correlated. In contrast, bird attack rates on live maggots and plasticine models were positively correlated, but did not show significant latitudinal changes.Main ConclusionsLatitudinal patterns in predation differ between major groups of predators and between types of prey. Poleward decreases in both arthropod and combined arthropod and bird predation on plasticine models do not mirror patterns of predation on our live prey, the latter likely reflecting real patterns of predation risk better than do patterns of attack on artificial prey

The natural drivers and the effects of landscape transformation for dragonflies of the Cape Floristic Region

Thesis (MSc)--Stellenbosch University, 2016.ENGLISH ABSTRACT: The Cape Floristic Region (CFR) is a biodiversity hotspot. The region has three established biosphere reserves, which all aim to alleviate the impacts that land transformation has on ecosystem integrity, without jeopardizing basic human needs. In addition to its unique plant diversity, the CFR has high endemism levels of other taxa, including dragonflies. Dragonflies are useful bioindicators of freshwater quality, which has led to the development of the Dragonfly Biotic Index (DBI), a biomonitoring tool for freshwater. The combined pressures of urbanisation and agricultural expansion in the CFR are a major concern for rare, endemic dragonfly species, as well as for overall river ecosystem integrity. In view of this, my study aims to determine which variables drive lotic dragonfly diversity in the CFR, and to assess the effects that land transformation has on this diversity. I first determined which environmental parameters were consistently important so that they could be used as mesofilters to conserve dragonfly diversity (Chapter 2). Dragonfly assemblages and various environmental variables were recorded along the untransformed reaches of three CFR rivers. Heterogeneity of water parameters was found to be the most crucial variables for dragonfly assemblages and for affecting species richness. Here, heterogeneity is defined by the natural spatial and temporal variation of water temperature, dissolved oxygen, conductivity and pH. This differed from previous studies, which strongly suggest vegetation-related variables are the primary drivers of dragonfly diversity. However, these studies took place in transformed landscapes where the strong effects related to anthropogenic disturbances could override the importance of other more subtle natural variables. The maintenance of a gradient of water parameters, which accounts for the natural range of each of the selected water variables, would thus aid in the conservation of dragonflies in the CFR. I also investigated the effects of urbanization and agricultural development on dragonfly diversity and DBI scores. Land transformation homogenized dragonfly assemblages as some endemic species could not persist in these areas. However, species richness was not always reduced, because disturbance allowed for additional widespread, generalist species to enter the system. Dragonfly assemblages differed between agricultural and urban sites but these sites were more similar to each other than to undisturbed sites. Each river supported a unique dragonfly assemblage, making it important to conserve each individual river. Mitigating the adverse influences of landscape transformation is essential for the conservation of rare and endemic taxa, particularly in areas of high conservation value, and the DBI provided an effective way to assess ecosystem integrity in the region. In conclusion, land transformation negatively affects dragonfly diversity and ecosystem integrity in CFR rivers. Conservation efforts should aim to rehabilitate the natural heterogeneity of riparian ecosystems. However, conservation plans should not only focus on restoration of riparian vegetation, but also incorporate variation in water quality parameters. There is not a high possibility of reducing land transformation, with the requirements of an ever-increasing human population. An important alternative option, as I show here, is to protect ecological integrity within a biosphere reserve. The proclamation of more biosphere reserves in the CFR, that include other, additional river catchments, will allow for the conservation of more rare, endemic dragonflies and other taxa. Dragonfly assemblages and the DBI should be used in future monitoring programs and to guide conservation actions.AFRIKAANSE OPSOMMING: Die Kaapse Floristiese Streek (KFR) is 'n biodiversiteit kernarea. Die streek besit drie gevestigde biosfeerreservate, wat poog om die impak van landtransformasie op die integriteit van ekosisteeme te verlig, sonder om basiese menslike behoeftes in gevaar te stel. Benewens sy unieke plantdiversiteit, het die die KFR ook besonderse hoë vlakke van ander endemisme taxa, insluitend naaldekokers. Naaldekokers is uiters nuttig as bioindikatos van varswater gehalte. Dit het geleei tot die ontwikkeling van die naaldekoker biotiese indeks (NBI), 'n biomoniterings hulpmiddel. Die gekombineerde druk vanaf verstedeliking en landbou-uitbreiding in die KFR is 'n groot bron van kommer vir die bewaring van skaars, endemiese naaldekokerspesies, sowel as vir algehele rivierekosisteem integriteit. In lig hiervan, het my studie gepoog om te bepaal watter spesefieke faktore naaldekokerdiversiteit dryf in die KFR. Die gevolge van land transformasie op hierdie diversiteit was ook geevalueer. Eerstens het ek bepaal watter omgewingsfaktore deurgaans belangrik is om naaldekoker diversiteit te bewaar (Hoofstuk 2). Naaldekoker gemeenskappe en verskeie omgewings-veranderlikes was aangeteken langs die ongetransformeerde areas van drie KFR riviere. Heterogeniteit van waterveranderlikes was bevind as die mees kritieke faktore wat naaldekoker gemeenskappe en spesierykheid bepaal. Hierdie resultate verskil van vorige studies wat gewys het dat plantegroei verwante veranderlikes die primêre oorsake van verandering van naaldekoker diversiteit is. Hierdie vorige studies was egter gefokus op getransformeerde landskappe waar die sterk effekte van menslike versteurings die belangrikheid van ander, meer subtiele, natuurlike faktore kon oorheers. Die instandhouding van 'n wye verskeidenheid water veranderlikes blyk dus om die behoud van die naaldekoker gemeenskappe in die KFR the bevorder. Ek het ook die gevolge van verstedeliking en landbouontwikkeling op die diversiteit van naaldekokers en die NBI bepaal. Landtransformasie het naaldekoker gemeenskappe gehomogeniseer deurdat sommige endemiese spesies nie kon bestaan in hierdie gebiede nie. Dit het egter nie altyd gepaard gegaan met ‘n vermindering in spesierykheid nie, want aandui dat addisionele, wydverspreide, generiese spesies versteurde habitatte binnedring. Naaldekoker gemeenskappe het tussen landbou en stedelike areas verskil, maar was steeds meer soortgelyk aan mekaar as aan ongestoorde areas. Elke rivier ondersteun 'n unieke naaldekoker gemeenskap, wat daarop wys dat dit belangrik is om elke individuele rivier te bewaar. Verligting van die negatiewe invloede van landskaptransformasie is noodsaaklik vir die bewaring van skaars en endemiese spesies, veral in gebiede van hoë bewaringswaarde. Die NBI verskaf 'n doeltreffende manier om die integriteit van die ekosisteem te evalueer in hierdie streek. Ten slotte, land transformasie beïnvloed naaldekoker diversiteit en die integriteit van die ekosisteem in KFR riviere negatief. Bewaring moet poog om die natuurlike heterogeniteit van die rivieroewer ekosisteme te rehabiliteer. Bewaring moet egter nie uitsluitlik fokus op die herstel van oewerplantegroei nie, maar moet ook poog om variasie in water faktore te inkorporeer. Vermindering van transformasie area is nie werklik haalbaar in die streek nie aangesien 'n toenemende menslike bevolking se vereistes ook toeneem. 'n Belangrike alternatiewe opsie, soos ek hier uitwys, is om te verseker dat die ekologiese integriteit binne biosfeerreservaate beskerm word. Die proklamasie van meer biosfeerreservate in die KFR, wat bykomende rivieropvanggebiede insluit, sal voorsiening maak vir die bewaring van meer seldsaame en endemiese naaldekokers, asook ander taxa. Naaldekoker gemeenskappe en die NBI behoort gebruik te word in toekomstige moniterings programme en kan dus bewaringsoptredes lei

Dragonflies as bioindicators and biodiversity surrogates for freshwater ecosystems

Thesis (PhDAgric)--Stellenbosch University, 2019.ENGLISH ABSTRACT: Biological indicators (bioindicators) are useful for rapid and cost-effective ecosystem assessments. Dragonflies are valued for their potential as bioindicators in freshwater ecosystems. My dissertation aims to assess and expand on their use as bioindicators in transformed landscapes and as surrogates for other aquatic biodiversity. Of the three bioindicator categories (environmental, ecological and biodiversity), biodiversity indicators and their application are poorly understood. The umbrella species concept is a biodiversity surrogacy method that aims to conserve a large number of species in an ecosystem by focusing on a select group of co-occurring species. I used the umbrella index, which quantitatively identified a group of seven dragonfly species and a group of eight Ephemeroptera, Plecoptera and Trichoptera (EPT) species, any of which could be used as biodiversity surrogates (Chapter 2). Adult dragonflies can only be surveyed on warm, windless days during summer, but are easily identifiable. On the other hand, their larvae can be sampled under any weather conditions and are also sensitive bioindicators. I showed that the interchangeability of the life stages for assessments was dependent on landscape spatial scale, coupled with the specific question asked (Chapter 3). Comprehensive biodiversity surveys at fine ecological scales should sample both adults and larvae. However, at larger spatial scales with coarser ecological questions, either adults or larvae can be used. To mitigate the detrimental effects caused by forestry, ecological networks (ENs) are integrated into plantation landscapes. These comprise grassland corridors connected to protected areas (PAs), which often include rivers. They aim to conserve biodiversity by creating habitats or facilitating dispersal of grassland species. I showed that water quality and adult dragonfly diversity did not differ between EN corridors and PAs (Chapter 4). Therefore, the EN approach is an effective method for conserving dragonfly diversity and river ecosystem integrity in plantation landscapes. In the Pietermaritzburg Botanical Gardens, an insect conservation pond was built along a degraded stream. Dragonfly species richness and abundance significantly increased, as both lentic and lotic species were able to colonize the area. Over time, the pond became overgrown and siltation reverted it back to a stream, which negatively affected dragonfly diversity. Shortly after extensive restoration efforts, the dragonfly assemblage had almost completely recovered and closely resembled that of the original pond. This was linked to alien plant removal, decreased vegetation cover and the inclusion of a range of microhabitats. This indicates that conservation ponds need to be actively maintained to keep their function as biodiversity reservoirs. This highlights the value of dragonflies as indicators of habitat quality in aquatic restoration projects. Throughout the thesis, adult dragonflies continuously demonstrated their success as bioindicators. The umbrella index validated the use of dragonflies as biodiversity indicators and surrogates for some of the most sensitive aquatic taxa (the EPT). Although dragonfly larvae and adults are both indicators of water quality, they are not always interchangeable, in terms of sampling at the species level. Their interchangeability depends on the specific question asked and the scale used. I also successfully monitored dragonfly assemblage responses in agricultural lotic and urban lentic environments, which highlighted their benefits for good aquatic conservation planning in transformed landscapes.Doctora

Ecological and Human Diet Value of Locusts in a Changing World

International audienceSince ancient times, locusts have been serious pests wreaking havoc on settled agriculture throughout much of the world. Numerous locust practices have been developed to control infestations. This has led to most commentaries portraying locust infestations only in a negative light while focusing on finding best management practices for suppressing locust populations and lessening crop damage caused by swarms. Yet, locusts are also of great ecological significance in being not only an extraordinary natural phenomenon but also major components of ecosystem nutrient cycling, arising long before settled agriculture. Furthermore, for humans, locusts are a nutritious food source, historically and currently being consumed directly. Locust control today should more regularly include their harvesting. This is now more feasible, as environmentally friendly biopesticides can be used to replace harmful organic pesticides. We focus here on the ecological significance of locusts by using calculations based on a 1 km 2 area of swarming and breeding Desert locusts, Schistocerca gregaria, and show that the huge biomass of locust individuals contributes greatly to ecosystem processes while also having great potential use in human nutrition, especially where there is an urgent need for improved dietary intake and nutrition

Ecological and Human Diet Value of Locusts in a Changing World

International audienceSince ancient times, locusts have been serious pests wreaking havoc on settled agriculture throughout much of the world. Numerous locust practices have been developed to control infestations. This has led to most commentaries portraying locust infestations only in a negative light while focusing on finding best management practices for suppressing locust populations and lessening crop damage caused by swarms. Yet, locusts are also of great ecological significance in being not only an extraordinary natural phenomenon but also major components of ecosystem nutrient cycling, arising long before settled agriculture. Furthermore, for humans, locusts are a nutritious food source, historically and currently being consumed directly. Locust control today should more regularly include their harvesting. This is now more feasible, as environmentally friendly biopesticides can be used to replace harmful organic pesticides. We focus here on the ecological significance of locusts by using calculations based on a 1 km 2 area of swarming and breeding Desert locusts, Schistocerca gregaria, and show that the huge biomass of locust individuals contributes greatly to ecosystem processes while also having great potential use in human nutrition, especially where there is an urgent need for improved dietary intake and nutrition

Ecological and Human Diet Value of Locusts in a Changing World

Since ancient times, locusts have been serious pests wreaking havoc on settled agriculture throughout much of the world. Numerous locust practices have been developed to control infestations. This has led to most commentaries portraying locust infestations only in a negative light while focusing on finding best management practices for suppressing locust populations and lessening crop damage caused by swarms. Yet, locusts are also of great ecological significance in being not only an extraordinary natural phenomenon but also major components of ecosystem nutrient cycling, arising long before settled agriculture. Furthermore, for humans, locusts are a nutritious food source, historically and currently being consumed directly. Locust control today should more regularly include their harvesting. This is now more feasible, as environmentally friendly biopesticides can be used to replace harmful organic pesticides. We focus here on the ecological significance of locusts by using calculations based on a 1 km2 area of swarming and breeding Desert locusts, Schistocerca gregaria, and show that the huge biomass of locust individuals contributes greatly to ecosystem processes while also having great potential use in human nutrition, especially where there is an urgent need for improved dietary intake and nutrition

Towards Global Volunteer Monitoring of Odonate Abundance

Insects are reportedly experiencing widespread declines, but we generally have sparse data on their abundance. Correcting this shortfall will take more effort than professional entomologists alone can manage. Volunteer nature enthusiasts can greatly help to monitor the abundance of dragonflies and damselflies (Odonata), iconic freshwater sentinels and one of the few nonpollinator insect groups appreciated by the public and amenable to citizen science. Although counting individual odonates is common in some locations, current data will not enable a global perspective on odonate abundance patterns and trends. Borrowing insight from butterfly monitoring efforts, we outline basic plans for a global volunteer network to count odonates, including organizational structure, advertising and recruiting, and data collection, submission, and synthesis. We hope our proposal serves as a catalyst for richer coordinated efforts to understand population trends of odonates and other insects in the Anthropocene

Predation on Live and Artificial Insect Prey Shows Different Global Latitudinal Patterns

International audienceAim Long‐standing theory predicts that the intensity of biotic interactions increases from high to low latitudes. Studies addressing geographic variation in predation on insect prey have often relied on prey models, which lack many characteristics of live prey. Our goals were to explore global latitudinal patterns of predator attack rates on standardised live insect prey and to compare the patterns in predation on live insects with those on plasticine prey models. Location Global forested areas. Time Period 2021–2023. Major Taxa Arthropods, birds. Methods We measured predation rates in 43 forested locations distributed across five continents from 34.1° S to 69.5° N latitude. At each location, we exposed 20 sets of three bait types, one set per tree. Each set included three live fly larvae (maggots), three live fly puparia and three plasticine models of the puparia. We used glue rings to isolate half of the sets from non‐flying predators. Results Arthropod attack rates on plasticine prey decreased linearly from low to high latitudes, whereas attack rates on maggots had a U shaped distribution, with the lowest predation rates at temperate latitudes and the highest rates at tropical and boreal latitudes. This difference emerged from intensive predator attacks on live maggots, but not on plasticine models, in boreal sites. Site‐specific attack rates of arthropod predators on live and plasticine prey were not correlated. In contrast, bird attack rates on live maggots and plasticine models were positively correlated, but did not show significant latitudinal changes. Main Conclusions Latitudinal patterns in predation differ between major groups of predators and between types of prey. Poleward decreases in both arthropod and combined arthropod and bird predation on plasticine models do not mirror patterns of predation on our live prey, the latter likely reflecting real patterns of predation risk better than do patterns of attack on artificial prey