Changes in Grauer's gorilla (Gorilla beringei graueri) and other primate populations in the Kahuzi-Biega National Park and Oku Community Reserve, the heart of Grauer's gorilla global range

Grauer's gorillas (Gorilla beringei graueri) have declined drastically across their range in eastern Democratic Republic of Congo (DRC). Survey data analysed in 2016 estimated a 77% decline in numbers between the mid- 1990s and 2016 and predicted that Kahuzi-Biega National Park (KBNP), and the contiguous Oku Community Reserve (OCR) held much of the global population. An estimate of 3800 Grauer's gorillas was made across its range at that time. Here, we publish the most extensive survey of Grauer's gorilla numbers to date, using nest counts from 230 line transects across KBNP and OCR to derive more accurate estimates of both gorilla and chimpanzee numbers. Gorilla numbers were estimated from line transects at 1,571 (95% confidence interval [CI]: 824–2,993) within KBNP and at 2,244 (95% CI: 1,471–3,422) in OCR. Eastern chimpanzee (Pan troglodytes schweinfurthii) numbers were estimated at 2,500 (95% CI: 1,804–3,462) in KBNP and 687 (95% CI: 472–999) in OCR. Estimates of total numbers for the survey area were 5,252 (95% CI: 3,687–7,481) Grauer's gorillas and 4,275 (95% CI: 3,322–5,502) eastern chimpanzees. Chimpanzee numbers were not significantly different from the estimates in the mid-1990s but the gorillas had significantly declined, mostly in KBNP. Modeled densities of these apes indicated that distances to mines, villages, or roads significantly explained part of the distribution of these apes, with higher densities also found in more rugged and remote sites. Other primates have all declined in this region, likely due to bushmeat hunting, especially the Endangered Ulindi River Red Colobus Piliocolobus lulindicus. These results confirm the negative impact of insecurity on Grauer's gorilla but indicate that the population declines may not be as great as previously feared. Using our revised gorilla density estimate we revise the original estimate of global numbers from 3,800 to 6,800 individuals

Cytomegalovirus distribution and evolution in hominines

Herpesviruses are thought to have evolved in very close association with their hosts. This is notably the case for cytomegaloviruses (CMVs; genus Cytomegalovirus) infecting primates, which exhibit a strong signal of co-divergence with their hosts. Some herpesviruses are however known to have crossed species barriers. Based on a limited sampling of CMV diversity in the hominine (African great ape and human) lineage, we hypothesized that chimpanzees and gorillas might have mutually exchanged CMVs in the past. Here, we performed a comprehensive molecular screening of all 9 African great ape species/subspecies, using 675 fecal samples collected from wild animals. We identified CMVs in eight species/subspecies, notably generating the first CMV sequences from bonobos. We used this extended dataset to test competing hypotheses with various degrees of co-divergence/number of host switches while simultaneously estimating the dates of these events in a Bayesian framework. The model best supported by the data involved the transmission of a gorilla CMV to the panine (chimpanzee and bonobo) lineage and the transmission of a panine CMV to the gorilla lineage prior to the divergence of chimpanzees and bonobos, more than 800,000 years ago. Panine CMVs then co-diverged with their hosts. These results add to a growing body of evidence suggesting that viruses with a double-stranded DNA genome (including other herpesviruses, adenoviruses, and papillomaviruses) often jumped between hominine lineages over the last few million years.Peer Reviewe

Assessing the Threat of Amphibian Chytrid Fungus in the Albertine Rift: Past, Present and Future

<div><p><i>Batrachochytrium dendrobatidis</i> (<i>Bd</i>), the cause of chytridiomycosis, is a pathogenic fungus that is found worldwide and is a major contributor to amphibian declines and extinctions. We report results of a comprehensive effort to assess the distribution and threat of <i>Bd</i> in one of the Earth’s most important biodiversity hotspots, the Albertine Rift in central Africa. In herpetological surveys conducted between 2010 and 2014, 1018 skin swabs from 17 amphibian genera in 39 sites across the Albertine Rift were tested for <i>Bd</i> by PCR. Overall, 19.5% of amphibians tested positive from all sites combined. Skin tissue samples from 163 amphibians were examined histologically; of these two had superficial epidermal intracorneal fungal colonization and lesions consistent with the disease chytridiomycosis. One amphibian was found dead during the surveys, and all others encountered appeared healthy. We found no evidence for <i>Bd</i>-induced mortality events, a finding consistent with other studies. To gain a historical perspective about <i>Bd</i> in the Albertine Rift, skin swabs from 232 museum-archived amphibians collected as voucher specimens from 1925–1994 were tested for <i>Bd</i>. Of these, one sample was positive; an Itombwe River frog (<i>Phrynobatrachus asper</i>) collected in 1950 in the Itombwe highlands. This finding represents the earliest record of <i>Bd</i> in the Democratic Republic of Congo. We modeled the distribution of <i>Bd</i> in the Albertine Rift using MaxEnt software, and trained our model for improved predictability. Our model predicts that <i>Bd</i> is currently widespread across the Albertine Rift, with moderate habitat suitability extending into the lowlands. Under climatic modeling scenarios our model predicts that optimal habitat suitability of <i>Bd</i> will decrease causing a major range contraction of the fungus by 2080. Our baseline data and modeling predictions are important for comparative studies, especially if significant changes in amphibian health status or climactic conditions are encountered in the future.</p></div

Prevalence of <i>Bd</i> positive genera in tested samples (CI, Wilsons score).

<p>Prevalence of <i>Bd</i> positive genera in tested samples (CI, Wilsons score).</p

Predicted future habitat suitability and <i>Bd</i> distribution in 2080.

<p>A. Illustrates the predicted current distribution and risk of <i>Bd</i> to amphibians in 2015 using all locations in the modeling (<i>Bd</i> records obtained in this study and previous studies [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0145841#pone.0145841.ref029" target="_blank">29</a>–<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0145841#pone.0145841.ref032" target="_blank">32</a>]). B. An average of the model output from the three General Circulation Models that shows the future distribution of where amphibians are likely to be at risk for <i>Bd</i> infection in 2080 under the A2a scenario. Our results predict a large range contraction of suitable habitat for <i>Bd</i> with future climate change.</p

Genera assessed for the disease chytridiomycosis that were also <i>Bd</i> positive by PCR.

<p>Genera assessed for the disease chytridiomycosis that were also <i>Bd</i> positive by PCR.</p

MaxEnt response curves illustrate how the likelihood for <i>Bd</i> occurrence is influenced by maximum temperature of warmest month (Bio5) and the mean annual precipitation (Bio12).

<p>A. Shows the probability of presence of <i>Bd</i> as it relates to Bio5 when all other environmental variables are kept at their average values. B. Shows the same as in A, except that Bio5 alone was used for model calibration. C. Shows the probability of presence of <i>Bd</i> as it relates to Bio12 when all other environmental variables are kept at their average values. D. Shows the same except that Bio12 alone was used for model calibration. The red line is the mean of 100 bootstrap runs with +/- one standard deviation (blue).</p

<i>Bd</i> prevalence in sampled amphibians in current or proposed protected areas throughout the Albertine Rift.

<p><i>Bd</i> prevalence in sampled amphibians in current or proposed protected areas throughout the Albertine Rift.</p