Are New Goat Species Evolving in New Zealand?
Goats (Capra hircus) were introduced to New Zealand by early European settlers. They were used as food, for their fur and as weed control. But some escaped and/or were deliberately released. They found many habitats in New Zealand to their liking and are now a pest in many parts of the North and South Islands, from sea level to the alpine zone.
It is in the alpine zone that the first signs of genetic differentiation have been observed. In the same way as goats in the European Alps are noted to be evolving, New Zealand’s alpine population also appears to be in the early stages of splitting into separate species.
Goats are well suited to life in alpine hills and mountains; they are sure-footed and can climb to find food in steep and difficult terrain. However, the easiest path to find new pasture on such steep hillsides is to follow the approximate contours of the hill or mountain so that they stay at about the same level; neither going up nor down the steep slopes to any large degree. Movement up or down can thus be achieved in small increments and with less energy required. Individuals that follow this sort of path are therefore more evolutionarily successful and pass on their genes to their next generation.
Populations in these regions are often isolated from other populations by the valleys and rivers between mountains and ranges. This isolation of small populations means a higher level of inbreeding and more rapid differentiation due to small, but beneficial, differences in habitat and behaviour.
Goats live in loose family herds and it has been noted, by hunters and observers of the feral goats, that in some locations the groups of goats only circumnavigate their territorial hills in one direction; clockwise* in some places and anti-clockwise* in others. There are some locations where these separate territories and populations can meet, usually at the higher reaches, above the river valleys, and where groups of hills or mountains join. But, when these populations meet, it has been observed that there is little or no interbreeding between the groups. It is thought that the goats that have developed the behaviour of travelling in a clockwise direction around mountains are not inclined to mate with those that travel in the opposite direction and vice-versa. On examination of hunted carcasses and captured animals, it has been found that goats that travel in the clockwise direction have right legs that are marginally (~5%) shorter than their left legs and goats that travel in an anti-clockwise direction have marginally (~5%) shorter left legs than right legs. These adaptations make the goats more sure-footed on the slopes when travelling in their chosen direction. But this may make breeding with the ‘opposite direction’ goats more difficult. This may be the first signs of the groups splitting into two different sub-species which, over time, could become fully separate species. The definition of separate species is organisms that are unable to mate. The different groups, in practicality, are able to mate on flat terrain but may be unable or unlikely to mate on steep terrain. Therefore, they may be, in a practical sense, differentiating into separate breeding populations that are leading to separate sub-species and eventually to separate species. Researchers have suggested Capra hircus dextro (clockwise goats)and Capra hircus sinistro (anticlockwise goats) for the current separate pseudo-sub-species.
Although there is less evidence for this, there is also a suggestion that two other sub-species may be evolving; Capra hircus deorsum (downward goats) and Capra hircus sursum (upward goats) for groups that have shorter hind legs (downward) and shorter forelegs (upward) groups.
It is hoped that more research into this fascinating evolutionary process will be funded soon.
*As mapped from above.
Note the date of publication - April 1st
P.s. This is the basis of the first genetics lecture I had at university. The purpose of the lecture was to encourage students to listen to the lecturer and not just write down notes of what the lecturer said without understanding or questioning what was being said.