PLANT HYBRID ZONES AS CENTERS OF BIODIVERSITY - THE HERBIVORE COMMUNITY OF 2 ENDEMIC TASMANIAN EUCALYPTS
PLANT HYBRID ZONES AS CENTERS OF BIODIVERSITY - THE HERBIVORE COMMUNITY OF 2 ENDEMIC TASMANIAN EUCALYPTS
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DOI：
10.1007/bf00325886
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发表时间：
1994-05-01
期刊：
影响因子：
2.7
通讯作者：
POTTS, BM
中科院分区：
文献类型：
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作者：
WHITHAM, TG;MORROW, PA;POTTS, BM
我们发现杏仁桉和里斯多桉之间的杂交带是昆虫和真菌物种丰富度和丰度的中心。在检查的 40 个类群中，73% 在混合区的丰度显着高于纯区，25% 没有显着差异，2% 在纯寄主物种中丰度最高。杂交树上的昆虫和真菌物种平均多出 53%，而且杂交树上的相对丰度平均比纯林中生长的桉树物种高 4 倍。杂交物种可能成为稀有物种的避难所：40 个物种中有 5 个物种主要局限于杂交区域。此外，50% 的物种仅在混合区中共存，形成了独特的物种组合。尽管杂种支持更多的物种和更大的丰度，但所有杂种并不相同：所检查的 40 个类群中，68% 的一种杂种表型的丰度显着高于另一种。虽然食草动物对 F1 型中间体的浓度很少，但在类似于杏仁 E. amygdalina 或 E. risdonii 回交的表型上浓度很常见。对于专门的食草动物来说，最常用的杂交表型似乎是由其与其宿主物种的表型亲和力决定的。通才在杂种上表现出总体上更大的丰富度，但不太可能利用一种杂种表型而不是另一种。对这些分布的机制解释有很多，并且可能是特定于物种的，但可能包括： 由于杂交破坏而导致杂交种的遗传易感性增加；杂交区的胁迫增加，导致植物易感性增加；混合区的资源更加多样化，可以支持更多的物种。杂交种及其亲本物种的种子荚产量与草食性呈负相关。然而，很难确定食草动物是否会导致这种模式，因为杂种可能本质上具有较低的有性生殖。为保护稀有和濒危物种而颁布的法律不包括杂交物种。我们认为有必要重新审查我们当前的“混合政策”。植物杂交区是植物进化和物种形成的中心，是重要经济植物和潜在生物防治剂的来源，而且正如我们的研究表明的那样，还为植食性群落提供了重要的栖息地。
We found the hybrid zone between Eucalyptus amygdalina and Eucalyptus risdonii to be a center of insect and fungal species richness and abundance. Of 40 taxa examined, 73% were significantly more abundant in the hybrid zone than in pure zones, 25% showed no significant differences, and 2% were most abundant on a pure host species. The average hybrid tree supported 53% more insect and fungal species, and relative abundances were, on average, 4 times greater on hybrids than on either eucalypt species growing in pure stands. Hybrids may act as refugia for rare species: 5 of 40 species were largely restricted to the hybrid zone. Also, 50% of the species coexisted only in the hybrid zone, making for unique species assemblages. Although hybrids support more species and greater abundances, all hybrids are not equal: 68% of the 40 taxa examined were significantly more abundant on one hybrid phenotype than another. While herbivore concentrations on F1 type intermediates were rare, concentrations were common on phenotypes resembling backcrosses either to E. amygdalina or E. risdonii. For specialist herbivores, the hybrid phenotype most heavily utilized appears to be determined by its phenotypic affinity to its host species. Generalists exhibit an overall greater abundance on hybrids, but are less likely to utilize one hybrid phenotype over another. Mechanistic explanations for these distributions are numerous and probably species specific, but are likely to include: increased genetic susceptibility of hybrids due to hybrid breakdown; increased stress in the hybrid zone resulting in greater plant susceptibility; and a greater diversity of resources in the hybrid zone which could support more species. Seed capsule production by hybrids and their parental species is negatively correlated with herbivory. However, it is difficult to determine whether herbivores cause this pattern as hybrids may have inherently lower sexual reproduction. Laws enacted to protect rare and endangered species do not include hybrids. We argue that a re-examination of our current ''hybrid policy'' is warranted. Plant hybrid zones are centers of plant evolution and speciation, sources of economically important plants and potential biocontrol agents, and, as our study suggests, also provide essential habitats for phytophagous communities.