Biodiversity exists at three different levels: diversity between ecosystems, between species, and within species. The genetic diversity that exists within a species is what enables the species to evolve and adapt. Many studies have shown that genetic diversity provides resilience against extinction.
Conserving biodiversity, then, means more than preventing the extinction of a species. It also means preventing loss of genetic diversity within that species.
One way of losing genetic diversity is when populations go extinct in a particular location and specific genetic lineages come to an end. Another way is when individuals in small and isolated populations become more strongly related to each other. It can lead to inbreeding depression – when offspring are less fertile and less likely to survive. This has been described for many species, including lions.
Conservation managers can intervene to support genetic diversity in a species. For example, to expand and restore the natural range of a species, managers can release individual animals in an area where they have previously gone extinct. Or if a population has become so small and isolated that its genetic health is in danger, managers may bring in new, unrelated individuals to mimic natural migration between populations.
In practice, though, these initiatives usually focus on the population or numbers of individuals. They don’t always take genetic information into account. That’s dangerous. When managers don’t choose genetically suitable animals, moving them to another population can fail. It can even have a negative influence on overall biodiversity.
In African wildlife management, individual animals for translocations are often sourced from South Africa. The country has many intensively managed parks, which regularly have surpluses of certain species. But shipping South African animals across the continent and reintroducing them far away from their original population could have adverse effects for biodiversity. If they integrate into resident populations at the target site, they may spread their genes there, influencing the genetic makeup of the local population. This could even lead to the loss of genetic adaptation to local environments. And if it happens on a large scale, across multiple localities, all populations could become similar.
When planning a translocation, the genetic makeup of both the source and target populations needs to be taken into account. Preferably, both populations should be from the same genetic lineage. In this way, the translocation resembles natural migration between populations.
Lion genetics
We recently published a scientific article in which we assess available genetic data and its implications for translocations in the lion.
The lion has been a popular subject for studying diversity on the genetic level. Lions are a species that many people know and care about, with a vast range throughout sub-Saharan Africa and into India. Genetic data show that lion diversity is distributed across four different evolutionary lineages: East Africa, Southern Africa, West/Central Africa, and India. The first two lineages are grouped together as the southern subspecies, while the latter two are grouped together as the northern subspecies. To conserve the lion in the long term, we need to conserve its genetic diversity.
In our study, we’ve listed 132 lion populations or conservation units and provided information on genetic assignment, uncertainty and suitability for translocation for each source and target combination.
To get a better insight into the extent and directions of lions being moved around the continent, we also mined trade data from the CITES Trade Database. This records all import and export permits for transboundary trade. There is additional information on the origin of the individuals and the purpose of the transport. The data show that in less than 40 years, over 1,000 individual live lions have been moved between countries, and into countries in which wild lions occur.
We then assessed whether, based on all genetic information that’s currently available, these transports were within or between genetic lineages. We identified three levels of suitability, based on the genetic differentiation between populations. We scored a translocation between subspecies as “unsuitable”, as well as a translocation of “captive” individuals, with unknown genetic background.
We concluded that the vast majority of the translocated lions would be scored as “unsuitable”. That is, they could be a risk to the genetic diversity of lions and to biodiversity more generally.
Integrating genetics in decision making
Even though genetic data may be unavailable for some populations, based on our understanding of lion diversity and known locations of the boundaries between different lineages, we can often infer which genetic group they belong to. So genetics can be taken into account, even when genetic data from a particular population is missing.
We hope that the three different suitability levels we’ve provided will help conservation managers to explore different options when making their decisions. We encourage them to follow the natural distribution of genetic diversity in the lion when searching for suitable source populations.
In management interventions there are many other factors that need to be taken into account too – ecological, behavioural and even political. Even though these factors are not taken into account here, we hope that our work provides guidance and support to integrate genetics in future management decisions.
It’s in the interest of the lion, as a species, to focus not just on the persistence of populations, but also on the underlying genetic diversity. This will increase its resilience and adaptability, which is necessary for long-term survival of the species.
