Population size and genetic diversity of Nigerian lions (Panthera leo)

Abstract:
High growth rate in human populations, agricultural developments and industrialization have impinged negatively on the natural habitats of most large carnivores, causing fragmentation, isolation and consequently reduction in population size. Lions (Panthera leo) that once roamed most parts of Southern Europe, Asia, the Middle East, North America, northern part of South America and most parts of Africa are today found only in parts of sub-Saharan Africa and at a single site in India. Even in these areas, they are increasingly confined to supposedly protected areas where their numbers are gradually decreasing. In West Africa, lions are found only in national parks, game reserves and zoological gardens. In Nigeria, the only areas known to still have wild lions are Yankari Game Reserve (YGR), in Central North East and Kainji-Lake National Park (KLNP), in the West. I investigated the trend of events into the decline of lions by reviewing lion articles as far back as possible with the aim of understanding variables responsible for their decline over the years. I employed the method of non-invasive sampling of faeces in this study to gather information about the population size of lions in Nigeria. However, studies that employ non-invasive sampling are often confronted with pitfalls due to degraded DNA and non-uniform distribution of sloughed intestinal cells of the focal species in the faeces, which can result in low genotyping success. It is therefore important to store samples in conditions that can preserve the minute DNA quantity in the faeces at the time of collection prior to laboratory analysis. I investigated which medium may be most appropriate for storage of lion faecal DNA, and I found that amplification success was highest for samples preserved in ethanol. I investigated the pattern of phylogeographic distribution of the Nigerian lions and lions in other parts of Africa and India. The aim was to understand the genetic make-up of the Nigerian lion within the West and Central African range so as to aid in future conservation and management decisions. I found that the two lion populations in Nigeria have different origins. Lions in YGR resemble more closely Cameroon lions while the population in KLNP resembles closely the lion population in Benin. Furthermore, I conducted a pilot study in YGR using lion faecal samples collected opportunistically along game viewing and patrol tracks to test the feasibility and reliability of obtaining DNA from faeces collected from a tropical environment to identify individuals. This method proved feasible as eleven individuals were identified from two polymorphic microsatellite loci. The feasibility of the pilot survey prompted the extension of the study to KLNP with the aim to estimate the population size and the level of gene flow that may exist between these two lion populations. I found that the number of individuals within YGR and KLNP are small and there was no evidence for gene flow between them. To secure the long-term persistence of wild lions in Nigeria will require immediate and concerted actions from state, national and regional stakeholders.

Popular Abstract in English

Lions (Panthera leo) have become known to be synonymous with wild Africa since its extinction from most parts of its former range (Europe, Asia and Southern America). Few people realize that anthropogenic activities have caused habitat loss, fragmentation and reduction in size to the lions, forcing them to the brink of extinction. Whenever out in nature, most tourists that visit national parks or game reserves spend most of their time searching for, or observing and admiring lions they have encountered. The lion, Africa’s most iconic species, has attracted so much admiration to itself as some countries or clubs have incorporated its picture on their logo or coat of arms (e.g. lion’s club international, United Kingdom of Britain, Northern Ireland, Estonia, and Kenya) to mention a few. Yet this prestigious species is in dire danger of extinction in near future if measures are not put in place. Currently the lion is being listed as “vulnerable” on the International Union for the Conservation of Nature (IUCN) Red List of Threatened Species. It is now classified as “Endangered” in West and Central Africa where their relict populations still exist. They have vanished from over 80% of their historic range, and currently they exist in only 28 countries in Africa and at one locality in India. And even within Africa only seven countries (Botswana, Ethiopia, Kenya, South Africa, Tanzania, Zambia and Zimbabwe) are believed to still have more than 1,000 lions in the wild. This alarming decline calls for a need to gather information on population size and level of gene flow that may exist within and between populations within the different countries that still harbor lions. This is vital in order to devise conservation and management measures for the long-term survival of the few populations left. This project was born out of a desire to know the number of lions that exist within Yankari Game Reserve (YGR) when I was employed there by the Leventis foundation in 2006 as a research officer. I got involved in discussion with some staff of the reserve to have an idea of the number of lions that exist there. All conversation was met with many different “guess estimates” of between 50-100 individual lions. And yet within a reserve with such a small landmass (2,244km2) there were too few encounters of lions when out in the field, if such number is assumed to exist. Thus we designed a survey to estimate the population size of the lions in YGR using direct count. During the period of one year of the survey, there were very few encounters of lions to make available analyzable data; but there was often encounter of lion foot-prints and faeces when we go out in the field for survey. Thus we resolved to the use of lion faecal collection after Ulf Ottosson consulted with Staffan Bensch and other members of the Molecular Ecology and Evolution Lab at the Department of Biology (Bengt Hansson and Mikael Åkesson). Through the review of articles and books we investigated the trend of events for the decline of lions. This was to establish the lion’s historical range as far back as possible by describing the decrease in the lion population with references to human population, anthropogenic effects and climatic events etc. By so doing we can understand the trend of events and thereby assist on devising means to overcome these factors to save the remaining population. Lion faeces were collected opportunistically along existing game viewing and patrol tracks within the Reserve and preserved in 99% ethanol prior to analysis in the laboratory. Although the use of faeces for population and genetic study appears promising, it has a number of pitfalls associated with it, because of degradation of DNA (low quantity and quality) in faeces, which can cause genotyping errors. Therefore we deemed it important to store faecal samples in conditions that can preserve the minute DNA quantity at the time of collection before laboratory analysis. We tested three preservatives and found that ethanol was better among the other preservatives used. We investigated the pattern of distribution and extent of overlap of lions in Nigeria and other parts of Africa and India in order to understand the genetic makeup of the Nigerian lion within the West and Central African range. This we did by analyzing lion sequence data obtained from Genbank with sequences from eight supposedly unrelated individual lions already identified from both YGR and KLNP. An investigation into the genetic makeup and phylogeographic history of the lions in Africa is important for understanding both the evolutionary processes affecting them as well as developing conservation strategies and thus make future management decisions easier. A pilot study was conducted within YGR to test the feasibility and reliability of obtaining quality DNA from faecal sample collected from a tropical environment to identify individuals. This method proved feasible and reliable, and eleven individuals were identified using two polymorphic microsatellite loci. The success of the pilot study prompted us to extend the study to the second protected area within Nigeria, Kainji-Lake National Park (KLNP) that still holds lions. The aim was to estimate the population size of lions within these two areas to gather information about the number of wild lions that still exist in Nigeria, and also to understand the level of gene flow that may exist between them. We found that about eight lions still exist in YGR, while ten individuals were estimated in KLNP. The two populations were found to exhibit signs of inbreeding with no sign of gene flow between them. The finding in this study is an important guide for the conservation of lions in Nigeria as well as those in the neighboring countries of Cameroon, Benin and Burkina Faso.