Poster: Food competition between wild and domestic herbivores

Encroachment by domestic herbivores in wildlife sanctuary Male Mahadeshwara Hills, Southern India.

This project applies DNA metabarcoding for conservation purposes. With this webpage I aim to provide some interactivity and extra background behind the poster I created for the PhD poster session organised by the Science Library and the MN faculty of the University of Oslo. Find me at the session to get a sticker with one of the images on the poster! 

The full poster can be found at the bottom of this page, but here is the abstract:

Wild herbivores are not only under pressure from habitat degradation and destruction, but also have to compete for resources with each other and with domestic animals. India has the world’s second largest livestock population, which is grazing many of India’s wildlife reserves. This is a major cause for concern as livestock has competitive advantage over the local wildlife. Therefore it is important for conservation purposes to understand the dietary niche partitioning between these herbivores.

DNA metabarcoding previously provided information about the dietary composition for a range of different animals and has been applied here to reconstruct the diet of herbivores present in the Malai Mahadeswa wildlife sanctuary, southern India. Faecal samples are collected in the Malai Mahadeswa wildlife sanctuary from a range of different herbivores, including: elephants, cattle, goats, muntjacs, buffalo’s, wild boars, and macaques. Analysis of the herbivore DNA present in these samples allows for robust identification of the species, while the plant DNA provides insight into the dietary composition. For this purpose, DNA metabarcoding primers targeting the herbivore taxa of interest, and the universal plant primer pair trnL g,h are used to amplify DNA from the collected samples.

The impact of livestock on wild herbivores is a global conservation concern. With increasing pressures on local wildlife from a range of different factors, DNA metabarcoding of faecal samples is a non-invasive method providing a wide variety of information that could prove vital for the preservation of biodiversity in wildlife sanctuaries.

Relative abundance of plant DNA in herbivore diet

This Sankey diagram is showing the flows from plant families to the herbivores.

The blocks indicate the relative abundance of reads per plant family in the total dataset (left) and per herbivore species (right). The herbivore blocks are colored based on the most prominent plant family in their diet.

Try hovering over the blocks and the links and notice the numbers that pop-up. Note: this unfortunately doesn’t work well on mobile phones..

The plant abundance data has first been normalised to relative abundance of plant DNA per sample. The plant taxa that make up less then 1% of the diet have been filtered out. And the rest of the plant abundance data per sample has been aggregated and averaged per herbivore species.

This means that each individual block on the right represents (almost) 100% of the diet of that particular herbivore species. Hovering over the flows in between the blocks gives you an indication of how much of that diet comes from a specific plant family.

The blocks to the left are then a sum of all of these proportions, and are therefore indicated with numbers higher then 100%; the total sum of all the relative abundances of the plant families (all the blocks on the left added together) = 942.1354

You can also change the placing of the nodes, dragging-and-dropping them in order to tease apart some of the flows. Feel free to play around! Just refresh the page if you want it back to the way it was.

Who competes with whom?

The following Sankey diagram is showing the same flows from plant families to the herbivores as the first one, but then grouped based on similarity of the diets. Here the herbivore blocks are coloured based on if they are domestic (purple) or wild (green) species.

This grouping shows which wild herbivores are potentially most affected by which domestic herbivores.

There is a dichotomy in the diets of the studied herbivores: some clearly eat more Poaceae (grasses), whilst others seem to prefer the Fabaceae (legumes), and a few have a mixed diet, such as goats, buffalo’s and sambar deer. This is in concurrence with the known feeding ecology of these animals, where they are categorised as folivores (leaf-eaters), frugivores (fruit-eaters) and mixed feeders, respectively.

Based on these data, it seems that the diet of elephants, wild boars and rabbits highly overlap with domestic cattle, whilst the macaques, the barking deer and porcupines seem to compete with goats.

The impact of livestock on wild herbivores is a global conservation concern. With increasing pressures on local wildlife from a range of different factors, DNA metabarcoding of faecal samples is a non-invasive method providing a wide variety of information that could prove vital for the preservation of biodiversity in wildlife sanctuaries.

For these Sankey diagrams, I have used the neworkD3 package created for R; also described here: https://towardsdatascience.com/using-networkd3-in-r-to-create-simple-and-clear-sankey-diagrams-48f8ba8a4ace

The full poster, created for the 2019 PhD poster session of the MN faculty, UiO

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