I wish I was clever enough to understand what this statement means, I haven't got a clue.
Semnopithecus is the genus within which the Grey Langur is placed. Previously, it was believed that there was only one species -
Semnopithecus entellus - with a number of subspecies. As a result, the European population was managed at a species-level with most individuals in captivity being of no known subspecies - some of these may have been pure individuals of one or more subspecies, but with unknown origins, and many will have been introgressive hybrids between subspecies.
One of the few collections which did not hold generic individuals was ZSL London Zoo - this collection held Tufted Gray Langur (
Semnopithecus entellus priam), and continued to do so until 5 years ago. Within a year or two the remaining collections holding pure individuals went out of the taxon, leaving only the generic population.
However, by this point in time the scenario had got more complicated - two taxa which had previously been classed within
Trachypithecus - the Purple-faced Langur and Nilgiri Langur - were both merged into
Semnopithecus. Furthermore, the vast majority of subspecies within
Semnopithecus entellus had been granted full species status in 2001.
As such, rather than the remaining "grey langur" population being representative of one species, and merely not being determined down to subspecific level, it is now apparent that the individuals remaining in Europe represent a hybrid swarm of anywhere up to seven species:
Nepal (
Semnopithecus schistaceus)
Kashmir (
Semnopithecus ajax)
Tarai (
Semnopithecus hector)
Northern Plains (
Semnopithecus entellus)
Black-footed (
Semnopithecus hypoleucos)
Southern Plains (
Semnopithecus dussumieri)
Tufted (
Semnopithecus priam)
As it is possible that the eventual faltering of the Tufted population in Europe - along with other pure species - was due to a lack of genetic variety and inbreeding within the population, my previous statement was intended to reflect the fact that as the individuals which are soon to arrive at ZSL London Zoo represent hybrid forms - referred to as
Semnopithecus entellus (sensu lato) - and are therefore somewhat more varied genetically, it is possible that they will prove of more hardy stock.
There is a single Semnopithecus individual in Europe which is not part of this hybrid swarm - an ageing Nilgiri Langur (
Semnopithecus johnii) - but as this taxon has only recently been recognised as congeneric with the Grey Langur, it is not relevant to the matter at hand.