Research
05/29/14 12:21 PM

Lynx faces an extinction vortex

A downward spiral, wich is like a vortex.
A downward spiral, wich is like a vortex.

The Iberian Lynx can be in a so called 'extinction vortex', an spiral that inevitably would lead to its disappearance if extraordinary measures are not taken to avoid their genetic impoverishment and deterioration, says a CSIC's research. Genome sequencing of this feline will be a step in this direction.

The extinction vortex comes from the idea that the combination of a number of factors like the habitat loss, coupled with substantial changes in the living area –for example the rabbit health problems, that directly affected lynxes as their main pray--  and other situations can downsize populations and bring them to a point of no return, which means that the species can't recover and they collapse.

One consequence of being a small population is the high average of mates between relatives and, accordingly, the increase of inbreeding, which reduces the inhabitants genetic quality and diversity. These animals are more vulnerable to diseases and have more difficulties to cape with changes in their environment because they could have loose genetic information needed to preform the adaptation --such as it would have been the capability to survive in case of a sudden drop of temperatures through a change in their body fat.--

Furthermore, as a result of this process each time generations is weaker and, at the end, the species gets to an unstoppable path of extinction, even if all external factors that have started this process would disappear.

The research, published in Conservation Biology magazine, is headed by Francisco Palomares, in collaboration with José Antonio Godoy; Alejandro Rodríguez; Severine Roques; Mireia Casas-Marce; Eloy Revilla; José Vicente López-Bao and Miguel Delibes, all of them related to the Estación Biológica de Doñana.

The existence of an extinction vortex has been proved in some species of invertebrates, but not in vertebrates up to now due to the lack of historic data. Therefore, lynx's case could be the first studied and established.

Scientist has found that in the protected area of Doñana, in the South of Spain, the number of females is shrinking as well as the size of litters, although in contrast the age in which youngsters become independents has increase. In parallel, the natural mortality rates are rising, so that is compensating the decrease of car hits in the railways in the surrounding area.

According to the research, the changes in the sex average and youngsters dispersion can be random, although the lower size of litters and the growing rates of mortality could be a consequence of inbreeding. The worsening situation in both aspects, genetic and demographic, "can explain the failure of the conservation efforts for the Iberian Lynx," Palomares says in the paper published in Conservation Biology.

To reach to these conclusions researchers has analysed the life of the Iberian Lynx over a 25 year-period in Doñana en its surroundings. Specifically, the studied data related to 150 felines who lived between 1983 and 2008, reviewing the evolution of mortality rates (excluding deaths caused by car accidents, traps or those who where shot); comparing the litters sizes; analysing the offspring survival average and the edge when they become independent and leave their mothers to find their own territory. Sex proportion has been revised also.

In addition, there were analysed samples of biological tissues to establish the evolution of the genetic variation over 25 years. Specifically scientist evaluated the diversity in some genes that are important in the immunity response to illness.

Demographic data were collected through captures of Iberian lynxes, radio tracking and monitoring footsteps, as well as images from trap-cameras and the revision of dens during the reproduction and breeding period. As for the genetic information, comes from blood and tissue samples removed from captured or death lynxes and also from individuals preserved in museums.

Mortality multiplied by 10

The researchers grouped the information in two main periods, from 1983 to 1998 and between 2002 and 2008. They established that mortality rates have increased with a factor by 10 in the second phase.

Besides, the number of lynxes in each litter has decreased, in fact while in the first stage the average was 3,1 individuals for female a year, in the most recent phase declined to 2,2, which is 27% contraction.  It has been ruled out that this evolution has nothing to do with a scarcity of food, because the studied areas were plenty of rabbits.

Downsizing litters involve new risks for the lynx population, because apart from the diversity lose, the relation between sex could be seriously altered. Furthermore, this can lead to the point in wich during some years only males would be borned, with catastrophic results.

Unfortunately, nowadays in Doñana the lynx population is far from the accurate sex ratio, wich is a balanced proportion between females and males. This latest condition was fulfilled before 1998 but then things changed and reciently there ara more females. Demographically speaking, if the equality among sex is 0,5 the male average is today 0,3.

Another important founding is that lynxes live shorter lives now. The survivance ration in adults has dropped sharply off from 75% to an average of 61%. In contrast, youngsters increasingly leave the litter before to settle in their own territory. At the beginning of the study females becomes independent when they reach 3 year-old but now they abandon their mothers one year before, while in males the age has fallen from 4 yerars old to only one.

More and more similar

The researchers grouped the information in two main periods, from 1983 to 1998 and between 2002 and 2008. They established that mortality rates have increased with a factor by 10 in the second phase.

Besides, the number of lynxes in each litter has decreased, in fact while in the first stage the average was 3,1 individuals for female a year, in the most recent phase declined to 2,2, which is 27% contraction.  It has been ruled out that this evolution has nothing to do with a scarcity of food, because the studied areas were plenty of rabbits.

Downsizing litters involve new risks for the lynx population, because apart from the diversity loose, the relation between sex could be seriously altered. Furthermore, this can lead to the point in which during some years only males would be born, with catastrophic results.

Unfortunately, nowadays in Doñana the lynx population is far from the accurate sex ratio, which is a balanced proportion between females and males. This latest condition was fulfilled before 1998 but then things changed and recently there are more females. Demographically speaking, if the equality among sex is 0,5 the male average is today 0,3.

Another important founding is that lynxes live shorter lives now. The survival ratio in adults has dropped sharply off from 75% to an average of 61%. In contrast, youngsters increasingly leave the litter before to settle in their own territory. At the beginning of the study females becomes independent when they reach 3 year-old but now they abandon their mothers one year before, while in males the age has fallen from 4 years old to only one.

More and more similar

As for the genetic diversity, in 2008 at least 70 % of the ancestors of the 23 adults studied lynxes came from the area of Coto del Rey, within the National Park , indicating a high degree of inbreeding. Genetic analyses have confirmed this decline and have found that there is what is called ' loss of heterozygosity ' a phenomenon by which the two existing copies of each gene (each copy comes from one parent ) are becoming most often identical , which means a higher probability to suffer genetic defects.

Finally, in the last few years it was been confirmed a high presence of disease which indicates that lynxes are more vulnerable to illness. After this analysis the scientist concludes that this specie is on an extinction vortex, and that specific measures might be a priority to try to avoid it.

The scientists are now towards this measures, that began in 2007 with the first shipment of a lynx from the Andújar population to Doñana's.

Available languages: Spanish
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