diff --git a/src/isomorphic/hooks/ReactComponentTreeHook.js b/src/isomorphic/hooks/ReactComponentTreeHook.js
index 29840438a21ee..e6998b08d93c5 100644
--- a/src/isomorphic/hooks/ReactComponentTreeHook.js
+++ b/src/isomorphic/hooks/ReactComponentTreeHook.js
@@ -16,9 +16,46 @@ var ReactCurrentOwner = require('ReactCurrentOwner');
 var invariant = require('invariant');
 var warning = require('warning');
 
-var itemByKey = {};
-var unmountedIDs = {};
-var rootIDs = {};
+function isNative(fn) {
+  // Based on isNative() from Lodash
+  var funcToString = Function.prototype.toString;
+  var hasOwnProperty = Object.prototype.hasOwnProperty;
+  var reIsNative = RegExp('^' + funcToString
+    // Take an example native function source for comparison
+    .call(hasOwnProperty)
+    // Strip regex characters so we can use it for regex
+    .replace(/[\\^$.*+?()[\]{}|]/g, '\\$&')
+    // Remove hasOwnProperty from the template to make it generic
+    .replace(
+      /hasOwnProperty|(function).*?(?=\\\()| for .+?(?=\\\])/g,
+      '$1.*?'
+    ) + '$'
+  );
+  try {
+    var source = funcToString.call(fn);
+    return reIsNative.test(source);
+  } catch (err) {
+    return false;
+  }
+}
+
+var itemMap;
+var itemByKey;
+
+var canUseMap = (
+  typeof Array.from === 'function' &&
+  typeof Map === 'function' &&
+  isNative(Map)
+);
+
+if (canUseMap) {
+  itemMap = new Map();
+} else {
+  itemByKey = {};
+}
+
+var unmountedIDs = [];
+var rootIDs = [];
 
 // Use non-numeric keys to prevent V8 performance issues:
 // https://github.com/facebook/react/pull/7232
@@ -30,18 +67,24 @@ function getIDFromKey(key) {
 }
 
 function get(id) {
+  if (canUseMap) {
+    return itemMap.get(id);
+  }
   var key = getKeyFromID(id);
   return itemByKey[key];
 }
 
 function remove(id) {
+  if (canUseMap) {
+    itemMap.delete(id);
+    return;
+  }
   var key = getKeyFromID(id);
   delete itemByKey[key];
 }
 
 function create(id, element, parentID) {
-  var key = getKeyFromID(id);
-  itemByKey[key] = {
+  var item = {
     element,
     parentID,
     text: null,
@@ -49,6 +92,12 @@ function create(id, element, parentID) {
     isMounted: false,
     updateCount: 0,
   };
+  if (canUseMap) {
+    itemMap.set(id, item);
+    return;
+  }
+  var key = getKeyFromID(id);
+  itemByKey[key] = item;
 }
 
 function purgeDeep(id) {
@@ -144,10 +193,6 @@ var ReactComponentTreeHook = {
 
   onBeforeMountComponent(id, element, parentID) {
     create(id, element, parentID);
-
-    if (parentID === 0) {
-      rootIDs[id] = true;
-    }
   },
 
   onBeforeUpdateComponent(id, element) {
@@ -163,6 +208,9 @@ var ReactComponentTreeHook = {
   onMountComponent(id) {
     var item = get(id);
     item.isMounted = true;
+    if (item.parentID === 0) {
+      rootIDs.push(id);
+    }
   },
 
   onUpdateComponent(id) {
@@ -184,9 +232,14 @@ var ReactComponentTreeHook = {
       // got a chance to mount, but it still gets an unmounting event during
       // the error boundary cleanup.
       item.isMounted = false;
+      if (item.parentID === 0) {
+        var indexInRootIDs = rootIDs.indexOf(id);
+        if (indexInRootIDs !== -1) {
+          rootIDs.splice(indexInRootIDs, 1);
+        }
+      }
     }
-    unmountedIDs[id] = true;
-    delete rootIDs[id];
+    unmountedIDs.push(id);
   },
 
   purgeUnmountedComponents() {
@@ -195,10 +248,11 @@ var ReactComponentTreeHook = {
       return;
     }
 
-    for (var id in unmountedIDs) {
+    for (var i = 0; i < unmountedIDs.length; i++) {
+      var id = unmountedIDs[i];
       purgeDeep(id);
     }
-    unmountedIDs = {};
+    unmountedIDs.length = 0;
   },
 
   isMounted(id) {
@@ -292,10 +346,13 @@ var ReactComponentTreeHook = {
   },
 
   getRootIDs() {
-    return Object.keys(rootIDs);
+    return rootIDs;
   },
 
   getRegisteredIDs() {
+    if (canUseMap) {
+      return Array.from(itemMap.keys());
+    }
     return Object.keys(itemByKey).map(getIDFromKey);
   },
 };
diff --git a/src/renderers/shared/hooks/__tests__/ReactComponentTreeHook-test.js b/src/renderers/shared/hooks/__tests__/ReactComponentTreeHook-test.js
index 28f3d931a14dd..7cf97ca1cef52 100644
--- a/src/renderers/shared/hooks/__tests__/ReactComponentTreeHook-test.js
+++ b/src/renderers/shared/hooks/__tests__/ReactComponentTreeHook-test.js
@@ -46,14 +46,19 @@ describe('ReactComponentTreeHook', () => {
       }
     }
 
-    function expectWrapperTreeToEqual(expectedTree) {
+    function expectWrapperTreeToEqual(expectedTree, andStayMounted) {
       ReactComponentTreeTestUtils.expectTree(rootInstance._debugID, {
         displayName: 'Wrapper',
         children: expectedTree ? [expectedTree] : [],
       });
+      var rootDisplayNames = ReactComponentTreeTestUtils.getRootDisplayNames();
+      var registeredDisplayNames = ReactComponentTreeTestUtils.getRegisteredDisplayNames();
       if (!expectedTree) {
-        expect(ReactComponentTreeTestUtils.getRootDisplayNames()).toEqual([]);
-        expect(ReactComponentTreeTestUtils.getRegisteredDisplayNames()).toEqual([]);
+        expect(rootDisplayNames).toEqual([]);
+        expect(registeredDisplayNames).toEqual([]);
+      } else if (andStayMounted) {
+        expect(rootDisplayNames).toContain('Wrapper');
+        expect(registeredDisplayNames).toContain('Wrapper');
       }
     }
 
@@ -64,12 +69,12 @@ describe('ReactComponentTreeHook', () => {
 
       // Mount a new tree or update the existing tree.
       ReactDOM.render(<Wrapper />, node);
-      expectWrapperTreeToEqual(expectedTree);
+      expectWrapperTreeToEqual(expectedTree, true);
 
       // Purging should have no effect
       // on the tree we expect to see.
       ReactComponentTreeHook.purgeUnmountedComponents();
-      expectWrapperTreeToEqual(expectedTree);
+      expectWrapperTreeToEqual(expectedTree, true);
     });
 
     // Unmounting the root node should purge
@@ -1854,4 +1859,107 @@ describe('ReactComponentTreeHook', () => {
       ReactDOM.render(<Foo />, el);
     });
   });
+
+  describe('in environment without Map and Array.from', () => {
+    var realMap;
+    var realArrayFrom;
+
+    beforeEach(() => {
+      realMap = global.Map;
+      realArrayFrom = Array.from;
+
+      global.Map = undefined;
+      Array.from = undefined;
+
+      jest.resetModuleRegistry();
+
+      React = require('React');
+      ReactDOM = require('ReactDOM');
+      ReactDOMServer = require('ReactDOMServer');
+      ReactInstanceMap = require('ReactInstanceMap');
+      ReactComponentTreeHook = require('ReactComponentTreeHook');
+      ReactComponentTreeTestUtils = require('ReactComponentTreeTestUtils');
+    });
+
+    afterEach(() => {
+      global.Map = realMap;
+      Array.from = realArrayFrom;
+    });
+
+    it('works', () => {
+      class Qux extends React.Component {
+        render() {
+          return null;
+        }
+      }
+
+      function Foo() {
+        return {
+          render() {
+            return <Qux />;
+          },
+        };
+      }
+      function Bar({children}) {
+        return <h1>{children}</h1>;
+      }
+      class Baz extends React.Component {
+        render() {
+          return (
+            <div>
+              <Foo />
+              <Bar>
+                <span>Hi,</span>
+                Mom
+              </Bar>
+              <a href="#">Click me.</a>
+            </div>
+          );
+        }
+      }
+
+      var element = <Baz />;
+      var tree = {
+        displayName: 'Baz',
+        element,
+        children: [{
+          displayName: 'div',
+          children: [{
+            displayName: 'Foo',
+            element: <Foo />,
+            children: [{
+              displayName: 'Qux',
+              element: <Qux />,
+              children: [],
+            }],
+          }, {
+            displayName: 'Bar',
+            children: [{
+              displayName: 'h1',
+              children: [{
+                displayName: 'span',
+                children: [{
+                  displayName: '#text',
+                  element: 'Hi,',
+                  text: 'Hi,',
+                }],
+              }, {
+                displayName: '#text',
+                text: 'Mom',
+                element: 'Mom',
+              }],
+            }],
+          }, {
+            displayName: 'a',
+            children: [{
+              displayName: '#text',
+              text: 'Click me.',
+              element: 'Click me.',
+            }],
+          }],
+        }],
+      };
+      assertTreeMatches([element, tree]);
+    });
+  });
 });
diff --git a/src/renderers/shared/hooks/__tests__/ReactComponentTreeHook-test.native.js b/src/renderers/shared/hooks/__tests__/ReactComponentTreeHook-test.native.js
index bdfedebd48948..bdbf4c549c4a0 100644
--- a/src/renderers/shared/hooks/__tests__/ReactComponentTreeHook-test.native.js
+++ b/src/renderers/shared/hooks/__tests__/ReactComponentTreeHook-test.native.js
@@ -70,14 +70,19 @@ describe('ReactComponentTreeHook', () => {
       }
     }
 
-    function expectWrapperTreeToEqual(expectedTree) {
+    function expectWrapperTreeToEqual(expectedTree, andStayMounted) {
       ReactComponentTreeTestUtils.expectTree(rootInstance._debugID, {
         displayName: 'Wrapper',
         children: expectedTree ? [expectedTree] : [],
       });
+      var rootDisplayNames = ReactComponentTreeTestUtils.getRootDisplayNames();
+      var registeredDisplayNames = ReactComponentTreeTestUtils.getRegisteredDisplayNames();
       if (!expectedTree) {
-        expect(ReactComponentTreeTestUtils.getRootDisplayNames()).toEqual([]);
-        expect(ReactComponentTreeTestUtils.getRegisteredDisplayNames()).toEqual([]);
+        expect(rootDisplayNames).toEqual([]);
+        expect(registeredDisplayNames).toEqual([]);
+      } else if (andStayMounted) {
+        expect(rootDisplayNames).toContain('Wrapper');
+        expect(registeredDisplayNames).toContain('Wrapper');
       }
     }
 
@@ -88,12 +93,12 @@ describe('ReactComponentTreeHook', () => {
 
       // Mount a new tree or update the existing tree.
       ReactNative.render(<Wrapper />, 1);
-      expectWrapperTreeToEqual(expectedTree);
+      expectWrapperTreeToEqual(expectedTree, true);
 
       // Purging should have no effect
       // on the tree we expect to see.
       ReactComponentTreeHook.purgeUnmountedComponents();
-      expectWrapperTreeToEqual(expectedTree);
+      expectWrapperTreeToEqual(expectedTree, true);
     });
 
     // Unmounting the root node should purge