Variation in extinction risk among birds: Chance or evolutionary predisposition?
Variation in extinction risk among birds: Chance or evolutionary predisposition?
复制标题
DOI：
10.1098/rspb.1997.0057
复制
发表时间：
1997-03-22
影响因子：
4.7
通讯作者：
Owens, IPF
中科院分区：
文献类型：
--
作者：
Bennett, PM;Owens, IPF
Collar et al.（1994）估计，在现存的9672种鸟类中，有1111种濒临灭绝。在这里，我们测试这些受威胁的物种是否只是鸟类的随机样本，还是它们的生物学特性使它们容易灭绝。我们问三个具体的问题。首先，灭绝风险是随机分布在家庭中的吗？第二，哪些科（如果有的话）包含的受威胁物种比偶然预期的多或少？第三，灭绝风险的分类群之间的差异是否与体型或繁殖力的差异有关？灭绝的风险并不是随机分布在不同的家族中。受威胁物种数量明显高于预期的科是鹦鹉科、野鸡科、信天翁科和信天翁科、秧鸡科、鹤科、秧鸡科、秧鸡科、秧鸡科、秧鸡科、秧鸡科、秧鸡科、秧鸡科、秧鸡科和鸽子科。唯一一个受威胁物种明显少于预期的科是啄木鸟（Picidae）。灭绝风险也不是随繁殖力或体型随机分布的。一旦系统发育得到控制，灭绝风险的增加与体型的增加和繁殖力的下降独立相关。我们认为，这是因为数千万年前进化出来的低繁殖率，使某些谱系容易灭绝。如果将低繁殖力种群减少到较小的规模，则需要更长的时间才能恢复，因此，如果外力导致死亡率上升，从而扰乱繁殖力和死亡率之间的自然平衡，则更有可能灭绝。
Collar et al. (1994) estimate that of the 9672 extant species of bird, 1111 are threatened by extinction. Here, we test whether these threatened species are simply a random sample of birds, or whether there is something about their biology that predisposes them to extinction. We ask three specific questions. First, is extinction risk randomly distributed among families? Second, which families, if any, contain more, or less, threatened species than would be expected by chance? Third, is variation between taxa in extinction risk associated with variation in either body size or fecundity? Extinction risk is not randomly distributed among families. The families which contain significantly more threatened species than expected are the parrots (Psittacidae), pheasants and allies (Phasianidae), albatrosses and allies (Procellariidae), rails (Rallidae), cranes (Gruidae), cracids (Cracidae), megapodes (Megapodidae) and pigeons (Columbidae). The only family which contains significantly fewer threatened species than expected is the woodpeckers (Picidae). Extinction risk is also not distributed randomly with respect to fecundity or body size. Once phylogeny has been controlled for, increases in extinction risk are independently associated with increases in body size and decreases in fecundity. We suggest that this is because low rates of fecundity, which evolved many tens of millions of years ago, predisposed certain lineages to extinction. Low-fecundity populations take longer to recover if they are reduced to small sizes and are, therefore, more likely to go extinct if an external force causes an increase in the rate of mortality, thereby perturbing the natural balance between fecundity and mortality.