[N] 2006 Unbalanced food webs after K/Pg extinction
Wilf, P., Labandeira, C.C., Johnson, K.R. & Ellis, B. (2006) Decoupled Plant and Insect Diversity After the End-Cretaceous Extinction Science Vol. 313 no. 5790 pp. 1112-1115
Abstract : Food web recovery from mass extinction is poorly understood.We analyzed insect-feeding damage on 14,999 angiosperm leaves from 14 latest Cretaceous, Paleocene, and early Eocene sites in the western interior United States. Most Paleocene floras have low richness of plants and of insect damage. However, a low-diversity 64.4-million-year-old flora from southeastern Montana shows extremely high insect damage richness, especially of leaf mining, whereas an anomalously diverse 63.8-million-year-old flora from the Denver Basin shows little damage and virtually no specialized feeding. These findings reveal severely unbalanced food webs 1 to 2 million years after the end-Cretaceous extinction 65.5 million years ago.
New fossil evidence shows that at certain times and places, plant and insect diversity were severely out of balance, not linked as they are today. According to Peter Wilf one of the authors the K/Pg caused major extinction among North American plants and insects. The Western Interior U.S. was a dead zone for plants and plant-insect food webs. Right after the extinction, for 800,000 years, there was very low insect predation and plant diversity. We know those 9 million years afterwards, there was renewed diversity in both plants and insects. \\\\\\\"In modern forests, insect diversity tracks plant populations. If there are few plants, there are few insects, and that is what we expected to see and mostly found throughout the 10-million-year Paleocene. However, we looked extremely hard to test this conventional wisdom and found some shocking exceptions that have given us new ideas about how food webs recover from mass extinction.\\\\\\\", Wilf said.
Through most of the intervening Paleocene, most floras have low richness of plants and insect damage. Typical numbers of species of plants in the Paleocene range between 15 and 20 at the sites, with many of the same species found throughout the Paleocene. Insect predation was low as well. However, the team also found two unusual early Paleocene sites. The first, a previously identified site in the Denver basin, in the town of Castle Rock , showed great plant diversity, especially when compared with the other Paleocene floras. The second site, known as Mexican Hat, in southeastern Montana was even more intriguing. Looking at more than 2,000 specimens at Mexican Hat the researchers found the usual 16 species of plants, but the insect mines were unlike anywhere else in North America . At Mexican Hat the researchers found heavy and diverse insect damage; all abundant species were mined, and the four major species each showed more than one kind of mining. This kind of flora with incesct feeding tracks are not seen anywhere else in North America, not even in the Cretcaceous, before the extinction.
The K/Pg extinction may have destroyed the ecological links in the food web. Plants and insects were killed outright, and herbivorous insects took a further hit when the plants they were specialized to eat disappeared. Surviving insects faced the choice of shifting their food resource or dying. Many died, but in most places a few survived, and from these, some evolved to feed on new host plants. The authors suggests that temporally and geographically isolated occurrences of severely unbalanced food webs may be a widespread feature of ecological recovery from mass extinction, resulting from instability, incumbency and opportunism in drastically simplified ecological landscapes.
Abstract : Food web recovery from mass extinction is poorly understood.We analyzed insect-feeding damage on 14,999 angiosperm leaves from 14 latest Cretaceous, Paleocene, and early Eocene sites in the western interior United States. Most Paleocene floras have low richness of plants and of insect damage. However, a low-diversity 64.4-million-year-old flora from southeastern Montana shows extremely high insect damage richness, especially of leaf mining, whereas an anomalously diverse 63.8-million-year-old flora from the Denver Basin shows little damage and virtually no specialized feeding. These findings reveal severely unbalanced food webs 1 to 2 million years after the end-Cretaceous extinction 65.5 million years ago.
New fossil evidence shows that at certain times and places, plant and insect diversity were severely out of balance, not linked as they are today. According to Peter Wilf one of the authors the K/Pg caused major extinction among North American plants and insects. The Western Interior U.S. was a dead zone for plants and plant-insect food webs. Right after the extinction, for 800,000 years, there was very low insect predation and plant diversity. We know those 9 million years afterwards, there was renewed diversity in both plants and insects. \\\\\\\"In modern forests, insect diversity tracks plant populations. If there are few plants, there are few insects, and that is what we expected to see and mostly found throughout the 10-million-year Paleocene. However, we looked extremely hard to test this conventional wisdom and found some shocking exceptions that have given us new ideas about how food webs recover from mass extinction.\\\\\\\", Wilf said.
Through most of the intervening Paleocene, most floras have low richness of plants and insect damage. Typical numbers of species of plants in the Paleocene range between 15 and 20 at the sites, with many of the same species found throughout the Paleocene. Insect predation was low as well. However, the team also found two unusual early Paleocene sites. The first, a previously identified site in the Denver basin, in the town of Castle Rock , showed great plant diversity, especially when compared with the other Paleocene floras. The second site, known as Mexican Hat, in southeastern Montana was even more intriguing. Looking at more than 2,000 specimens at Mexican Hat the researchers found the usual 16 species of plants, but the insect mines were unlike anywhere else in North America . At Mexican Hat the researchers found heavy and diverse insect damage; all abundant species were mined, and the four major species each showed more than one kind of mining. This kind of flora with incesct feeding tracks are not seen anywhere else in North America, not even in the Cretcaceous, before the extinction.
The K/Pg extinction may have destroyed the ecological links in the food web. Plants and insects were killed outright, and herbivorous insects took a further hit when the plants they were specialized to eat disappeared. Surviving insects faced the choice of shifting their food resource or dying. Many died, but in most places a few survived, and from these, some evolved to feed on new host plants. The authors suggests that temporally and geographically isolated occurrences of severely unbalanced food webs may be a widespread feature of ecological recovery from mass extinction, resulting from instability, incumbency and opportunism in drastically simplified ecological landscapes.