Beetles, allies of our crops and bioindicators

The beetles (of which We already talked not long ago), protagonists of phobias and apparently annoying in agriculture, have demonstrated that they can be much more than just an insect.

What is a bioindicator?

BIO stands for “life” or “living organism”.

A bioindicator is a living organism capable of providing information on the characteristics of the environment or ecosystem in which it is found. For example, tree bark lichens are bioindicators of moisture, just as coleopterans, commonly called beetles, are indicative of the health of a habitat, such as crops.

Did you know that a crop, however artificial it may seem given its exploitation and modification by human beings, is also an ecosystem?

About Coleoptera

Coleoptera are the most diverse order of insects, with around 370,000 described species belonging to about 200 families, making them one of the animal groups with the greatest evolutionary success. They show holometabolic development, that is, they present a complete metamorphosis in which they go through 4 well-differentiated stages of development: egg, larva, pupa and imago or adult (Zarazaga, 2015).

Coleopteran ecology

Coleoptera have a very diverse ecology, which has allowed them to colonize a wide variety of environments that are very different from each other. On the other hand, they also have very varied dietary habits and establish a multitude of types of interactions with other living beings, which means that they are key elements in terrestrial ecosystems, performing essential ecological functions (Pearson & Cassola, 1992).

Eco-friendly functions

In terms of ecological functions, the decomposition of organic matter and the mineralization of nutrients stand out, which is also of special relevance in agricultural systems, which carry out soil beetles, such as the Tenebrionidae family, which is of special interest for evaluating the impact of human activities (Crawford, 1991).

Another function of special relevance in agricultural systems is that of the biological control of pests carried out by some species of beetles, such as staphylinid Ocypus olens (Müller 1764) (Tortosa, 2022). This species preys, among other prey, on the pupae of olive flies (Bactrocera oleae Rossi, 1790) when they abandon the fruit to bury themselves, thus avoiding damage to the olive trees.

Why are beetles good bioindicators?

Recently, beetles have gained significant interest in conservation studies and are used as biological bioindicators since they are present in numerous habitats and are sensitive to environmental changes (Uehara, 2009). Edaph beetles, in particular, have a close relationship with the soil, which makes them good indicators of the quality of this habitat, since they are very sensitive to their characteristics, such as pH, salinity, temperature or humidity, since they play an important role in their physiology, diet, reproduction and development (Cárdenas et al. 2011; Zerbino et al. 2008). Abrupt changes in any of these physicochemical soil variables, such as changes induced by the absence of vegetation cover, can be fatal for the development and survival of these organisms, which is an indication that the soil is degrading and losing quality (Zerbino et al. 2008).

The order Coleoptera has been the subject of research in many studies to analyze the human impact on habitats and their environmental quality (Grandchamp et al. 2005; Heyborne et al. 2003; Rainio & Riemela, 2003). The beetles of the Carabidae family have been used as bioindicators of crop management, since they are found in all agroecosystems and have been observed to be predators of numerous pests (Holland & Luff, 2000). Coleoptera of the Scarabaeidae family have been used as bioindicators in a study of the degree of human impact on Amazonian rainforests, showing as a result that the number of species and individuals increased with anthropogenic disturbance (Otavo et al. 2013).

In conclusion, beetles are a key tool in the ecosystem, because on the one hand they can fight against possible pests that affect them and on the other, they can diagnose the state of their soil, which makes them essential since they can help prevent problems that we don't see. Who was going to tell us that such a small being could help us with something so big?

Bibliography

Alonso-Zarazaga, M.A. (2015). Insect Class: Order Coleoptera. IDE@-SEA Magazine, 55, 1-18.

CÁRDENAS, A. M., BUJALANCE, J. L., & HIDALGO, J. M. (2011). Assessment of darkling beetle fauna after implementation of an environmental restoration program in the Southern Iberian Peninsula affected by the Aznalcóllar toxic spill. Journal of Insect Science, 11 (1).

CRAWFORD, C.S. (1991). The community ecology of macroarthropod detritivores. Ecology of Desert Communities. University of Arizona Press, Tucson.

GRANDCHAMP, A. C., BERGAMINI, A., STOFER, S., NIEMELÄ, J., DUELLI, P., & SCHEIDEGGER, C. (2005). The influence of grassland management on ground beetles (Carabidae, Coleoptera) in Swiss montane meadows. Agriculture, Ecosystems & Environment, 110 (3-4), 307-317.

HEYBORNE, W.H., MILLER, J.C., & PARSONS, G.L. (2003). Ground dwelling beetles and forest vegetation change over a 17-year period, in western Oregon, USA. Forest Ecology and Management, 179 (1-3), 123-134.

HOLLAND, J. M., & LUFF, M. L. (2000). The effects of agricultural practices on Carabidae in temperate agroecosystems. Integrated Pest Management Reviews, 5 (2), 109-129.

OTAVO, S. E., PARRADO-ROSSELLI, Á., & ARI NORIEGA, J. (2013). Superfamily Scarabaeoidea (Insecta: Coleoptera) as a bioindicator element of anthropogenic disturbance in an Amazonian national park. Journal of Tropical Biology, 61 (2), 735-752.

PEARSON, D. L., & CASSOLA, F. (1992). World‐wide species richness patterns of tiger beetles (Coleoptera: Cicindelidae): indicator taxon for biodiversity and conservation studies. Conservation Biology, 6 (3), 376- 391.

RAINIO, J., & NIEMELÄ, J. (2003). Ground beetles (Coleoptera: Carabidae) as bioindicators. Biodiversity & Conservation, 12 (3), 487-506.ROMERO, R.O. (2015). The influence of soil management on soil beetle (Coleoptera) communities in the ZEPA-LIC La Serena and Sierras Perifericas (Badajoz, Spain). SEA Bulletin, 56, 291-299.

TORTOSA, A., DUFLOT, R., RIVERS‐MOORE, J., LADET, S., ESQUERRÉ, D., & VIALATTE, A. (2022). Natural enemies emerging in cereal fields in spring may contribute to biological control. Agricultural and Forest Entomology.

UEHARA-PRADO, M., BY OLIVEIRA FERNANDES, J., BY MOURA BELLO, A., MACHADO, G., SANTOS, A. J., VAZ-DE-MELLO, F. Z., & FREITAS, A. V. L. (2009). Selecting terrestrial arthropods as indicators of small-scale disturbance: A first approach in the Brazilian Atlantic Forest. Biological Conservation, 142 (6), 1220-1228.

ZERBINO, S., ALTIER, N., MORÓN, A., & RODRÍGUEZ, C. (2008). Evaluation of soil macrofauna in direct seeding and grazing production systems. Agroscience Uruguay, 12 (1), 44-55.

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