Major contributors to the eco-systems: Insects
Biba Jasmine is in conversation with Daniel Gruner, Entomology Professor at the University of Maryland, digging deeper into the fascinating insect kingdom and its ability to alter the structure of the and solve environmental problems.
Insects are a dominant group of organisms that are present in many of the harshest ecosystems on the globe. However, particular species in the group have restricted ranges of occurrence depending on their ability to adapt to a variety of environmental factors,both in terms of taxonomic diversity and ecological function.There are also a diverse group of insects present based on their adaptations to varied environmental conditions. The ability to respond to the environmental variable rapidly makes insects useful indicators of change, potential regulators of ecosystem conditions, frequent competitors with humans for ecosystem resources and vectors of human and animal diseases.
The exponential growth of the human population has meant that shortage of food is a very real global threat today.Among the many solutions being suggested to tackle this issue is one that entomologists have put forth of growing crops of insects for food—insects as a source of food to answer the global problem of food paucity.
Biba: Many of society’s needs can be addressed using insects and the field of entomology becomes even more critical today. What role do you think insects play across all levels of biodiversity?
Dr. Gruner: Insects, and arthropods in general, are “the little things that run the world”, as stated by E.O. Wilson. The sheer number of species greatly surpasses all other known multi cellular group and they are involved in nearly all of the ecosystem functions that support humanity. They are critically important pollinators for many of the food crops we consume,except for wind-pollinated grain crops like rice, wheat and corn. They process dead organic matter and contribute to nutrient recycling; some are predators or parasites of crop or household pests or disease vectors. Insects and arthropods are critically important food for other biodiversity components, such as birds and mammals, and they contribute to our well-being.
Biba: While we do have some basic knowledge, we don’t have enough information about how insects interact with the environment. Could you briefly explain to us about what happens when you remove an insect population from the environment?
Dr. Gruner: This depends greatly on the species and the environment in question. If we remove a mosquito, it may result in fewer bites and maybe, even lower the incidence of disease, making it hard to argue for the need for mosquitoes.However, many mosquitoes are also pollinators (particularly the males that do not bite) and are important food for birds and bats and, in their aquatic larval stages, for fish. Insects in bio diverse systems are involved in complicated linkages with other species and it is very hard to predict how the system will respond if a species is removed.
Biba: Environmental changes, especially those resulting from anthropogenic activities, affect many species in ways that alter the ecosystem and, perhaps, global processes. What do you think are the primary challenges involved in placing insect ecology in an ecosystem context that represents its effect on the ecosystem and the diversity of their adaptations and responses to environmental conditions?
Dr. Gruner: This is a broad and difficult question. Changes in land use, the widespread use and misuse of chemical pesticides, and industrial-scale agriculture, greatly alters the local species composition and biodiversity, causing wide swings in abundance and outbreaks of pest species on crops.Outbreaks are relatively rare in systems not so affected by human activities. These are, thus, problems of our own making that are difficult to diagnose and ‘treat’ when so many different causes potentially interact and confound each other. For example, an insect outbreak might occur because crop plants are bred for higher yield varieties that have less chemical and structural defenses against the pests. They are grown in mono culture that gives these pests an abundant,easily found resource that allows them to feed and multiply in great numbers. The natural enemies (predators, parasites)that regulate pest populations may be more sensitive to chemical pesticides, or else they do not share a habitat in the mono culture to regulate the prey sufficiently. They do not have habitat in the mono culture where they can establish sufficient numbers to regulate their prey. All these problems amplify and work together to create a much larger problem to solve.
Biba: What according to you are the environmental conditions that both affect and reflect insect community structure?
Dr. Gruner: This is a very broad question, and the answer, invariably,is: it depends. Different species and insect communities are sensitive to different environmental conditions depending on their life histories and the other species with which they interact. For instance, wetland-dependent species will be very sensitive to droughts that may affect the permanence of their habitat. This may lead to the evolution of traits that support the retreating into dormant phases during a drought, or else strong movement abilities to find another wetland. Tropical species will have very different adaptations than those species that live on a mountain with a very short ice-free growing season. Broad climatic trends in rainfall and temperature are often predictive of the particular bio me in a place, and those conditions and the plants themselves, set the table for the insect communities in that habitat.
Biba: What according to you are the basic and applied goals of insect ecology?
Dr. Gruner: Broadly speaking, insect ecologists study the patterns of abundance and distribution of insects in relation to other species and the environment. The ‘applied’ goals of insect ecology are essentially to solve the problems affecting humanity–finding ways to manage bed bugs, or crop pests,or disease vectors such as mosquitoes. Very often, there are strong links between theory and application. By developing mathematical theory for insect outbreaks and testing these with long-term data, we may learn how to control those outbreaks by targeting certain life stages, managing their habitat, or by encouraging natural enemies as biological controls.
Biba: Insects have been recognized for their capacity to engineer ecosystem change, making them ecologically and economically important. Could you elucidate on that?
Dr. Gruner: The so-called ‘ecosystem engineers’ are species that modify their physical habitat in ways that affect other species. The classic example of this is the American beaver,which builds dams on small streams, fundamentally changing the hydrology and the species composition of their local ecosystem. Many insects do this, too, in important ways. Ants and termites, for example, build large nests and process large quantities of organic matter, and promote soil formation, thus altering decomposition rates and promoting bio geo chemical cycling. The structures they create – mounds or underground nests – are often used by other species, even while the ants and termites are still in residence! This happens on smaller scales with gall-forming insects, leaf rollers and tiers, and those that bore into twigs and stems creating cavities that other species use.
Biba: Insects respond to multiple factors simultaneously, not just one or a few factors subject to experimental manipulation,and their responses reflect trade offs that might not be reflected in studies that control only one or a few of these factors. What is your thought on framing research to evaluate insect responses to, or effects on, ecosystem conditions that should address a greater range of ecosystem variables than which has been commonly used in past insect ecology studies?
Dr. Gruner: We live in exciting times, with many new tools available to inform basic insect ecology. For example, we can now use data from remote sensing – from satellites, planes and small unmanned ‘drones’ – to measure large phenomena,and then link these patterns to on-ground ecology. We can also gather exceedingly detailed data, for example, by sequencing the stomach contents or even fecal matter of particular insects to determine the species in their diet. So, we now have unprecedented abilities to work with scientists in other fields and ask questions that were out of reach just 5-10 years ago.
Biba: How can this information be incorporated into management decisions and environmental policy?
Dr. Gruner: Well, this clearly depends on the questions we wish to ask. For example, by using genomics to investigate diets, we can use the data collected to construct a network model – much like we would in analyzing data from Facebook or Twitter – and essentially draw a map of all the feeding relationships in an insect community. This might help us with an applied question such as, ‘what prey do beetles consume in my field of crops?’‘How much of my target pest do they consume, and how much do they consume other things, including other beneficial insects?’
Biba: What advice would you give people who want to study insect ecology?
Dr. Gruner: The study of insect ecology starts with being curious about the creatures that are all around you, in your fields, along your walk to work or to school, even in your homes. It starts with asking questions about what these species do, and where and when they are found. Many children start with this curiosity naturally, but most are eventually taught to fear or avoid insects. We need to nurture and cultivate these young scientific minds and help them to ask and answer their questions, From there, any student can study entomology,ecology, and mathematics and volunteer to assist students and faculty in their research.
Biba: The aspects of entomology include human understanding of agriculture on human and animal health,biology, and even criminology in the form of forensic entomology. What all professions, according to you, can a professional entomologist seek?
Dr. Gruner: A trained entomologist can pursue academic research and teaching as I have done, or many other paths as well. Some entomologists work with farmers to develop sustainable strategies for ‘integrated pest management’:that is, a holistic approach to control economic pests using crop rotations, habitat management, biological controls, and sometimes, chemicals (the more targeted and sustainable,the better). Other entomologists work in the industry to control termites, bed bugs, or disease vectors in our homes,businesses and communities. They also strive to develop biologically informed strategies that minimize non-target impacts on beneficial insects and on human health.
This article first appeared in the March 2016 Saevus magazine.