Testudo graeca and Testudo marginata hybrids
The search for hybrids is one of the constants in breeding and agriculture. Man has always researched these intermediate forms and there are hybrids of plants and animals all over the world since we have dedicated ourselves to breeding and agriculture. Many, like common wheat or modern pigs, often don't even know they are. It must be clear that hybridizations occur spontaneously even in nature with a certain frequency and that often new species may arise from these events. It is therefore not an aberrant condition, on the contrary! We modern humans ourselves are the fruit and retain multiple hybridization events in our genome with other human species that have occurred throughout our evolutionary history. So all animals and plants. This clarification was necessary as many could turn up their noses and think that hybridizations are substantially deleterious and against nature, quite the opposite, they are one of the engines of evolution and allows to bring favorable characteristics from one organism to another, which otherwise they would be impossible. The human hand is often resolved in favoring encounters, which, however, in most cases occur accidentally, and above all in making selective pressure towards those resulting deemed more favorable or pleasant, so as to multiply and make them common. In the case of a farm, the search for hybrids has the sole purpose of adding variability, pleasant characteristics and perhaps greater resistance.
In fact, in our specific case of Testudo graeca and Testudo marginata, the chance encounter of these two species always produces fertile offspring and in turn fruitful, albeit with some evident limitations, at least in the first generation, which we will analyze in more detail below. Whether it is female Testudo graeca or vice versa male of this species and female Testudo marginata, the young that will be born will be easily recognizable as they will not have the characteristic triangles, let alone other spots. At birth, the plastron always appears to be devoid of any design, even if with the growth some references may appear, while color and design of the carapace, shape of the muzzle and distribution of the scales in the front legs, or the presence or absence of the typical spurs of the Testudo graeca, may vary from one individual to another.
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Notes and insights on Testudo hybrids
There is no exhaustive information on hybrids between the Testudo hermanni group and that of the Testudo graeca, only anecdotes, while those between the latter and the other two neighboring species, Testudo marginata and Testudo kleinmanni are frequent and well documented. Although Testudo marginata and Testudo kleinmanni can be considered genetically very close species, and therefore the theoretical possibility of hybridization is far from improbable, the absence of hybrids can be attributed to the huge difference in size, which in fact proves to be an insurmountable barrier for a natural match. In some cases I have heard of hybrids between Testudo hermanni and Testudo horsfieldii, but at present, I have no documented and reliable news of this possibility, only a few photos on the web. On the other hand, both species have similarities to each other, which are missing with the Testudo graeca group, therefore I do not consider it an unlikely situation.
Absolutely, the most frequent hybrids are those between Testudo graeca ibera x Testudo marginata as cross-breeds are recurrent. Babies are easily recognizable and have vigorous growth. Note that, while in Testudo marginata the dimensions between male and female are similar, in the hybrid the male remains significantly smaller than the female, like the Testudo graeca.
The little information about the hybrids of Testudo graeca x Testudo kleinmanni, is probably attributable to the rarity of this latter species and the fact that they are difficult to breed together, but on the other hand I have personally seen hybrids and have, albeit in small, the same characteristics of the Testudo marginata hybrid. The thing is not surprising, given the genetic closeness of the two species. The obstacle is purely dimensional, on the other hand, this is not to be considered impossible and with good probability, the offspring would be as fertile as or more than the other hybrids.
From pairs of Testudo hermanni and Testudo graeca, definitely not impossible given the low selectivity of the males of the latter species, I have personally observed births, however the chicks often present with serious malformations of the eyes and skull/jaw, as well as the limbs . The few reports indicate a high mortality at birth and only a few infants who survived, with difficulty, no more than one or two years. It should be noted that the search for hybrids often resolves on its own since the poor fertility and the long times to reach adulthood prevent us from exceeding two generations. At present, I can only certify the birth of a second generation, daughter of F1 generated by Testudo graeca ibera x Testudo marginata albino caramel. Mating was not natural, but it required artificial insemination, for another successfully succeeded.
F2 of Testudo graeca ibera x Testudo marginata albino T +
The attempt to obtain F1 hybrids, I started them in 2005 when I introduced a young female of Testudo graeca ibera born in 1994 in the enclosure of the Testudo marginata albino caramel. males of Testudo marginata in this albeit large tortoise. I therefore tried a different approach, artificially inseminating. Finally I had the first births. It should be noted that in the case of artificial insemination, the amount of sperm that can be sent to the female genital tract is extremely low and, contrary to the proverbial ability to produce fertile offspring for years, in these cases it is difficult to cover a single deposition season, but besides, I have never looked for numbers, but just a few specimens to test the possibility of obtaining hybrids that in F2 could generate albino offspring by virtue of the mutated gene of the Testudo marginata. Let's say that the 7 specimens that managed to reach the second year of life and born in 2008, the reason for this selection is attributable to predation by rats, are now part of a group of 4 males and 3 females now adults who have reached, in the case of females, imposing dimensions, touching the 30cm long carapace.
The first deposition was in 2016 which was followed by a single hatching which presented an important cranial malformation and the absence of the eyes, which evidently only passed the first winter. It should be noted that poor fertility in the primiparous is fairly normal, especially if the males are equally young, but nevertheless with these poor results. By 2017, the laying females had become 2 and despite more than 30 eggs, only one hatched with a perfectly formed baby, while another had an almost fully developed albino embryo. This was the first verification that the albino gene was perfectly functional even in hybrids. The following year, these two females always came to lay over 30 eggs. Unlike the previous year, there were 3 births, one of which was an albino. All the young were alive and well grown at the time of hibernation in autumn 2019. Again in this year, the births reached a record number of 4, of which two perfectly formed albinos and two specimens with abnormal scales. It should be noted that the viability of these specimens is at least equal, if not greater than the pure specimens. The problem is therefore the high percentage of hatching failures, even if the percentage of fertile eggs appear on the average of normal specimens. This suggests that the problem does not lie in the intrinsic fertility of animals, but rather in gamete problems, chromosomal aberrations or reassortments which lead to a high percentage of abortions. As in many similar cases, F1 appear to be scarcely fertile, while subsequent generations should regain fertility on a par with that observed in other animals. However I will not be able to answer this question before 8/10 years from now. It should be noted that the third female, meanwhile grown enormously and significantly more than the first two, having exceeded the 30cm long carapace, in the whole of 2019 she never laid. On the other hand, if it is true that Testudo graeca ibera lays on average 3 times a season and Testudo marginata also 4, these specimens stop at 1 or 2 at most, although numerous, counting on average a dozen eggs. Obviously the observations are limited to only 3 specimens, still young, and it will still take years to have a case study and observations of a certain significance.